Autumn 2003 p. 18

Interview with Gus Pfister, Pacific Fuel Injection, South San Francisco, CA

By LodeStar Editor, Brian Glusovich

The mechanical Fuel Injection pump used in the 6.3 M-100 engines is often thought of as the “heart” or the “brain” of the vehicles or, if not working right, just heartburn or headache. Even many knowledgeable German car mechanics blanch when they open the hood and see those intake tubes! Going through the MB Service Manuals, you quickly realize that this FI pump is not only an engineering marvel, but it’s almost an engine in itself. With its own camshaft, 8 plungers, direct cylinder injection, and a Machiavellian 3-dimensional camshaft for throttle control, it certainly qualifies as a “system”. Mechanical FI has been around at Mercedes since the 1930s, initially for diesel applications only. While FI was used on various aircraft during WWII, and on some 2-stroke gasoline engines after the war, it wasn’t used on an MB production car until the 300SL Gullwing. Over the years, the system began to be used on more of MB’s gasoline cars, since it allowed higher power for a given displacement, while attaining reasonable fuel economy. Variations of the direct port injection were used – the 220SE pontons used a twin-plunger injection pump

while the GM/Rochester system for Corvettes of the late 50s and early 60s had only one plunger for 8 cylinders [note in the interview that Gus refers to this as a “sprinkler” system]. The Corvette system was notoriously difficult to maintain, while MB systems, whether the 2 plunger variety or direct port injection (as on the 6.3 engines) has been relatively

low maintenance. It’s important to emphasize the “relatively” when mentioning the low maintenance; these systems do not generally require a lot of tuning or minor repairs, and can be counted on to perform reliably and consistently for long periods. However, when they need a rebuild, they will begin telling you with increasingly frequency and

volume: “Send me in for rehab!” In my own case, I’ve had my 6.3 for about 4 years now, and have pretty much zero information on what had been done to the car before I had it. I’d been noticing more oil collecting in the valley between service intervals, to the point where I was becoming worried

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about fire danger – additionally, I was getting a bit tired of cleaning out the valley every couple of weeks. My local mechanic determined that the pump was leaking from 2 solenoid seals, and one other seal. My local mechanic’s shop also indicated that they didn’t feel expert enough to handle the remove/replace and retuning of the FI unit. Thus, I went back to one of the M-100 experts in the Bay Area – Rene at Burlingame Motors. Rene has done a fair bit of work on my car, but he’s located about an hour from my house, so I’d been looking for someone a bit closer -- I had one for about 2 years until he retired and closed his shop. I know that’s a common problem with many of us. The guys who know M-100 vehicles are pretty scarce. Anyway, I brought it up to Burlingame Motors, and they pulled the pump, found that it was leaking both oil and gas, that the injectors looked OK, that it had never been in for a major rebuild, and needed one. So, off it went – I had a choice between Gus at Pacific Fuel Injection in South San Francisco and Robert at Fairchild Industries in Redding, CA. I didn’t, at the time, know if there more, but those two have been very highly recommended by a number of M-100 club members. We ended up sending to Gus because he’s located 10 minutes away from Rene’s shop. Well, the overhaul and reinstall was not a cheap event, but the results have been sensational. I thought the car was running well before (even with the oil leak), but now it’s amazingly smoother, stronger and even quieter! Plus, it looks like a little

gem sitting there in the middle of the engine, all plated and polished (see picture). I’m getting about 3-4 miles per gallon better now than before; in fact, on a 200 mile trip from San Jose to Cambria, I got 17 mpg – I’d been getting 11-12 before.

With this experience, I thought it might be interesting to interview Gus for the LodeStar. He’s been in the business of rebuilding these units for 35 years or so, and I figured he might help answer some of the questions which many members have raised, ranging from preventive maintenance items, pump longevity, and the prospect of getting parts and rebuild service in the future. I called Gus and he gladly agreed to an interview; in fact, he suggested we come in Saturday morning; he would open the shop for us, so we wouldn’t be disturbed by normal weekday activities. So, with my friend Jack Rosa doing photos, and my son Niko doing

video, we had a fascinating morning. It should be noted that the interview is not in any way a recommendation for Gus over his California competitor, Fairchild Industries. In fact, in speaking to both Robert and Gus, they seem to view each

other not as adversaries, but almost as co-dependents. We will likely do an interview with Robert in a coming issue, so we’d ask readers to send in questions and additional FI-related issues they’d like examined. LodeStar – I gather, from other material I’ve read, that you started about 35 years ago, in Switzerland? Gus -– Started with Lucas, competitor to Robert Bosch. LodeStar – What about these various brands -- Kugelfischer, Bosch, Lucas, etc? Didn’t this type of FI begin back in the 30s, with diesel engines? Gus -– Bosch systems started back in the 1920s, as a supplier to the other car companies, beginning with

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magnetos, and other electrical supplies. They’re still an independent company. They make many types of supplies for the OEMs – brakes, packing machines, FI systems, electrical. LodeStar – Kugelfischer was an independent company, weren’t they? What about Italian companies, like SPICA? Gus -– Yes, but they were bought out by Bosch, when the demand for mechanical FI units declined. SPICA was affiliated with Alfa Romeo. LodeStar – What about the injection systems used on American cars in the 1950s, like Corvette? Was that derived from these systems? Gus -– No, those are “sprinkler systems”, not actually an injection system – it sprinkles the fuel into the manifold – isn’t a timed injection as are these units. LodeStar – You moved to the U.S. in 1977, into Burlingame? Was a Bosch plant there, in Burlingame? Gus -– No, the Bosch plant was in South San Francisco. For repairing and training center, and for rebuilding gas injection systems. Bosch always rebuilt the diesel injection pumps themselves, until they dropped the business. We started out in Burlingame originally. The Bosch factory rebuild facility closed in 1979, because Bosch

didn't want to be in the business of repairing these pumps any longer. We then bought much of their equipment.

LodeStar – Did they all (diesel and gas) all go to electronic injection in the 1970s? Gus -– No, the diesel is only now going to electronic

injection. It’s called “rail injection”. They had these (show) up until 1999. The principle is the same up through today’s units, although

the newer systems are not really interchangeable. Here’s a unit from a large diesel turbine [e.d. – about 5 times the size of a 6.3 plunger]. From a locomotive, or ship diesel. For the 6 (or 8 or more) plungers, each pumps out through a check valve, pumps until the bottom end

opens, and the fuel will then run back into the pump.

LodeStar – How is the plunger mechanism lubricated? Gus -– The plunger mechanism is machined so precisely that there is no liquid passing through. LodeStar – How long a lifetime can the plunger have, for a car application? Gus -– 500,000 miles for the plunger unit. These will last almost indefinitely. LodeStar -- Is this unit from a 6.3?

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Gus – Yes, with the 8 plungers. Here is the controller, sleeve, segments. [Ed. Note – the video on the M-100 website will show how the pump elements are re-installed for a 6.3 pump]. LodeStar – (Looking at the surprisingly large camshaft), what usually breaks down first? Gus – Surprisingly, the most common problem is contaminated fuels. People lay their cars off, and the fuel corrodes the parts. LodeStar – That’s the term “Garages Kill” Gus – Yes, that’s certainly true. You look in the back here; we have many pumps from Porsches, Mercedes, and BMWs which we have gotten from cars which are not running any more LodeStar – Are there still

enough of the cars which people still want to keep running, to keep you going for twenty years or so? Gus – Difficult to say. Question of the future of gasoline and automobiles. LodeStar – Where do you get most of your pumps from, for service? Gus – Mostly from U.S., perhaps 5-10 a year from outside from U.S. Mostly Porsches and Mercedes, not so many BMWs any more. In the late 70s and early 80s, about 70-80% of Mercedes sales in the U.S. were diesels. The value of those cars today is not enough to justify a major overhaul of the fuel injection system. Also, on the gas injection cars, a lot of them are SEs, they may not be worth enough to make the overhaul

worthwhile. LodeStar – It looks like, with the labor involved, there is no way to do it on the cheap. Gus – Yes, that’s certainly true LodeStar – Are you able to get parts readily? Gus – I’m able to, but it’s generally much more economical to make use of used parts. We get a lot of parts from other shops which may have no use for them. I now have enough parts supply for the rest of my life.

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LodeStar – Now, you normally do these overhauls on the basis of a core exchange, don’t you? Someone sends in a pump, and you send it back? Gus – Not always – in fact, because of the poor shape most pumps come, and because of our large stock, we usually have a number of overhauled pumps ready to send out. LodeStar – Now, in the case of my own pump, which was recently sent in by Rene at Burlingame Motors? Gus – In that case, I rebuilt your pump. However, we have a number of 6.3 pumps here, about 20 to 30. LodeStar – Do you get a fair number of 6.3 pumps in for work? Gus – Yes, there are still a fair number of 6.3s around, but there were never as many to begin with, as the 6 cylinders. We do a lot of 230, 280SLs, 911s, and then some Kugelfischers, and some 6.3s. Still some diesels, also. LodeStar – You mentioned in one of the other articles I read about your shop, that you had a lot of difficulty in getting people to work on these old systems. Gus – Right now, there is just me and another older German fellow, a retired airline pilot. He’s been through the full training. To do this, you have to love detail work, and be able to live in the Bay Area. It’s just too expensive for most people. LodeStar – You’ve been here (1/2 mile north of the San Francisco airport, along the bay), for quite a while now. Gus – Yes, in this place since 1993, and before that in Burlingame.

LodeStar – Seals – are they the most common thing to go? Gus – Yes, and they’re all available still. LodeStar – Directly from Bosch? Gus – Yes, and there are other suppliers for some items. Many of these items can be made pretty readily. LodeStar – What gets ruined by bad gasoline, from not being run? Is it the seals? Gus – No, it’s the plungers. The seals get ruined by the heat. The seals will go out eventually, even if you drive your car every day. On the 6.3 the problem we have, is overfilling with oil. There’s an oil pressure line going to the injection pump, which actually only lubricates the plunger. LodeStar – And then you have a separate oil supply at the lower end…. Gus – That you have to add oil for. The lower end in the housing is sealed off by an O-ring. That O-ring gets hard. Then the oil starts flowing

down into the pump, and it gets overfilled. LodeStar – So, when this O-ring starts going out, is that when you start mixing the oil from the engine supply and the pump supply? Gus – No, the pump will actually fill up with oil, and overfill. LodeStar – Until you look at all these parts and how they fit in, you don’t understand how complicated this pump is. The height is deceptive when you look at the pump installed, because so much of the pump, with the cam, is hidden. Gus – Yes, that’s definitely true. Before, you were asking about the 3-dimensional cam. The throttle position, when you operate the throttle, will rotate the cam. With speed, you have flyweights, which will open and close the flyweights against the spring tension. And that will move the cam back and forth. Then you have the sensing roller – that senses the contours on the cam, and then moves up and down.

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LodeStar – And that’s lubricated by the lower end oil? Gus – Yes LodeStar – On mine, I guess the 3-dimensional cam had to be replaced. Is that just normal wear? Gus – Yes, just wear. You can only buy the cams from Bosch, but you can still get them. They’re $450. LodeStar – Are the newer diesel pumps similar to this? Gus – Not really – on the newer diesels with mechanical and electronic controls, you only control the idle speed and part way between idle and full throttle. Max RPM is electronically regulated on the diesel cars. On the gas cars, it is very important that you always have set the right air/fuel mixture at all throttle positions. LodeStar – This is a 6.3 unit, on the stand? [Ed. Note – Gus shows the assembly of the 6.3 unit on the video, which will be on the M-100 website] What is that step in the cam for Gus – Yes, this is a 6.3 unit. Note that the 3-d cam only turns about 80 degrees, so the step in the cam you were asking about is only for assembling, so it doesn’t cover the step. LodeStar – Where is this pump from? Gus – This is from an early 600. LodeStar – Looking at the MB shop manuals, they list about 5 different pump versions for the 6.3 engine. It seems that most of the changes relate to the 3-dimensional cam. Gus – Yes, most of the pump stayed the same over the years – the 3-d cam was what changed the most.

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LodeStar – Most of that was to do with emission controls? Gus -- Yes LodeStar – So, there aren’t really any significant changes in the pump over the years. Gus – The pump is always the same; it’s only the fuel map which is changed. LodeStar – When you mention the fuel map; for a person who wanted to set up a 6.3 engine for racing, or some other purpose? Is that what you’d change, the cam profile? Gus – It’s difficult to change the cam profile, although I do it pretty regularly for racing Porsches, and it’s mainly a full throttle adjustment. LodeStar – But it’s not like with Electronic FI, where you can modify the fuel/air mixture pretty readily. Gus – No; someone has to tell me pretty specifically what rpm range and what mixture he wants. LodeStar – Do you do it fairly often? Gus – Mostly for Porsche guys – Mercedes guys mostly stick to the way it is. Especially the 6.3, since it has so much power already. LodeStar – I know a fellow up in Washington State who uses his for drag racing. Would it make sense to modify the cam profile for that sort of use? Gus – If he gives me the numbers he wants for various rpm ranges, I can. All of this is approximation of what was done originally on an engine dyno. LodeStar – What is this table we’re at now?

Gus – This is a flow bench. We measure the fuel flow at various throttle positions and rpm settings. LodeStar – There’s only one other person in the U.S. that I know of who does these full scale overhauls. Fairchild up in Redding? Gus – Well, there is an outfit on the East Coast, called H&R, and there are some others who

do partial overhauls. LodeStar – This equipment from Bosch. I imagine it’s not available any more? Gus – No, since it’s used still for diesel pumps, so it’s still available from Bosch. Pretty expensive. LodeStar – This flow table is usable with any of the Bosch pumps? Gus – Yes, with slight adjustments. This is set up now for this 6.3 pump – I have to provide the oil myself, since the engine is not here.

LodeStar – So this oil won’t damage the seals. Gus – No, the seals get ruined from old age. If it overfills with oil, then the seals are already ruined. The oil will just come out where you add the oil. LodeStar – Before I sent mine I for overhaul, I was using a turkey baster to remove some of the excess oil from the dipstick hole.

Gus – Some filling up with oil is normal – the manual talks about that, and the need to drain it. LodeStar – On mine, I found that the valley was filling up with a combination of oil and gas. Gus – It should be cleaned at each oil change. When you have to clean it out between regular oil changes, than that’s a good time to consider an overhaul.

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LodeStar – That dipstick is certainly not easy to get to.

Gus – No, it sure isn’t. LodeStar -- Gus – Notice you have 3 springs in here, to work against the flyweights. The one in the center is the softest, regulates the speed up to about 1,000 rpm. Then the 2nd spring regulates up to about 1,500 rpm, and the 3rd, strong spring, regulates from about 1,500 on up. The spring tension can be adjusted by screws. The trick is

to bring the cam in for smooth transitions, at the right places. LodeStar -- Gus – This is the famous screw, you’re never supposed to adjust when the engine is on. Frequently the pumps come to us, where the mechanics have tried to adjust the fuel mixture when the engine is running. When you

push the screw in, it engages with the center. LodeStar – And it tears up the center screw Gus – Yes; if you’re lucky enough, it will engage with the slot while the engine is turning, it’ll turn out the adjusting screw immediately. Then the mechanic realizes something’s wrong. Then he tries to turn these screws back in, but it’s out of the thread. If he then tries to turn it in, he cross-threads the screw – then it’s locked completely, and they call us, saying “I haven’t touched anything”.

LodeStar – Wasn’t me! Gus -- LodeStar – Now, this is the idle mixture control, not the speed control Gus -- Right LodeStar – And it should never be adjusted while the engine is running, even though It’s sitting right out there, so it looks like a natural to go for Gus – That’s correct.

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LodeStar – Is there anything unique about this specific pump? Gus – All the Bosch gas pumps are very similar. Only Porsche, Mercedes and some Aston Martins use the 8 plunger pumps. A very few Aston Martins and the racing Porsches. Aston Martin pumps were in the engine valley, but the Porsches were flat eights. LodeStar – (watching) Gus – Now we’re pretty much ready to run the pump on the flow table. It’s set up pretty much like it is in the car. We have the fuel supply going through the pump, from the tank, through the injectors, and then we can measure the fuel flow in these graduated tubes. The machine will automatically

count the number of injection strokes I’ve set it for. Usually we use 500 or 1,000 injection strokes. We can use this at different throttle positions and engine rpm, measuring fuel flow at each point. LodeStar – [ed. Note – at this point, Gus started up the test bench, and it became hard to hear the tape recording – however, we could clearly see the results of the measurements in the graduated cylinders, for the various throttle positions and rpm readings.] Gus -- LodeStar – The pump is running at engine speed? Gus – No, it runs at one half engine speed. We take an idle reading, at 300 rpm pump

speed LodeStar – How much adjusting do you normally have to do at this point? Gus – In almost every case, we have to do a lot of fine tuning, to get the flow levels within tolerance (less than 2%). LodeStar – On a pump from a 6.3, or a 600 in this case, assuming it’s been maintained reasonably well, and driven regularly, how long should the pump last? Gus – 200,000 miles generally. LodeStar – So, it’s not a 70,000 mile or so thing generally Gus -- No LodeStar – Besides watching the oil, what other preventive maintenance items should we do? Other than driving it.

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Gus – The pump is pretty much maintenance free. LodeStar – When you get done with this, and send it back, with the flow setting correct, what about the other normal tuning things, like idle mixture and so on? Do you leave that back to the mechanic who re-installs the unit? Gus – I make sure the pump is delivering the right amount of fuel, at the right rpm, and the right throttle position. But on a gas engine, it’s really important you have the right air/fuel mixture, and the linkage has to be set right. LodeStar – So, it’s not a do-it-yourself job for most people, to take it out, send it in, and re-install…. Gus – It’s a pretty big job, and depends on the mechanical skill you have. You have to time it carefully when you put it back in – The pump only turns at ½ the engine speed, so you can actually install the pump 180 degrees off, and you still shows the right timing, but the pump is actually in the wrong stroke. You don’t want to inject fuel when the valves are closed, of course. The car still will run, but will hesitate quite a bit. Frequently, then the mechanic will richen the mixture to cover up the problem. That’s a problem with this system – you can actually cover up some problems by just running too rich. LodeStar – I’ve noticed that many mechanics, even mechanics trained on newer Mercedes, don’t want to touch these units. Gus – Definitely – you’ve got to be familiar with the manual. And even with that, it’s not really easy. Even some dealers

decline to work on these. They may have some guys who go back to the old days, but there are fewer and fewer. You need someone who has a personal interest in the older cars. LodeStar – So, if you’re in the middle of Nevada, or somewhere like that…. Gus – Recommendations – these people know each other. Or go to the Mercedes Benz club LodeStar – How long a job to overhaul and calibrate a normal unit? Gus – It’s normally about an 8 hour job. LodeStar – Now, you also plate various pieces. Is that for longevity or looks or… Gus – It’s for both – it looks nice and prevents the parts from corroding. Cadmium or zinc chrome. We have a number of plating shops locally. LodeStar – So, most of the parts, the consumable parts that you have to replace in a given rebuild – do you keep those in stock?

Gus – We have most parts here (showing a 2,000 square foot, or so, storage area, with shelves floor to ceiling). LodeStar – How many of these do you do in a normal month? Gus – 30 or so a month, and we have a backlog. LodeStar – The housing – does it get plated or treated? Gus – If it is pretty bad, it gets sandblasted. Otherwise, just cleaned. LodeStar – Can you clean the injectors? Gus – Yeah, we can ultrasonically clean them, with the unit we have here. We measure the opening pressure of the injectors. Then check the spray pattern. Then check to make sure the injector can hold pressure. LodeStar – Do you normally get the injectors, with the pumps? Gus – Not always, but often. If there is a definite miss or you suspect a problem, the injectors are something to look at.

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LodeStar – What if there was a fuel pressure regulator problem? At higher fuel pressure, what sort of things would happen? Gus – You need a certain amount of pressure feeding into the pump, and on the 6.3, you have a little pressure valve which is actually on the fuel dampener outlet – it’s not on the pump itself, people don’t usually send it. Those are pretty much maintenance free, however. The pump definitely needs a certain level of fuel pressure. LodeStar – What about too much fuel pressure? Gus – Too much really doesn’t hurt the pump. It’s possible too much might break a fuel line, but I’ve never seen that happen. LodeStar – For keeping the injectors clean, are any of these additives, like Techron, any good? Gus – That was a problem with carbureted engines, but with fuel injection today, they’ve reformulated the gasoline, so shouldn’t need those additives. LodeStar – The injectors are also pretty expensive, aren’t they? Gus – Yes, new ones are $800-900, but we can rebuild them here. The solenoid is readily available, and the check valve I usually rework. LodeStar – Is this what they talk about modifying, for hot starting or vapor lock problems? Gus – If you have hot starting problems, yes. The 6.3 also has different type of starting circuit. LodeStar – They have recommended changing the cold start valve, so you can get

a cold start squirt even when the engine is warm. Gus – If you have hot starting problems you can add a relay which also injects fuel through the cold start valves. LodeStar – What about mixture settings as the pump ages? Gus – As the units get older, it tends to run richer. With wear, the pump will compensate toward richer. You can adjust the fuel flow, but if you stop getting results, it’s probably time to have the unit rebuilt, meaning there’s too much wear. LodeStar – And for adjusting? Gus – There are different mechanisms for adjusting the fuel – first you can adjust the idle mixture screw (with engine OFF), then the lower partial load screw (the black screws). These are adjusted in pairs. Do not touch the white screws. LodeStar – Turning it in makes it richer? Gus – Yes, and the next thing you can do is adjust the control rack, which adjusts the fuel map over the whole range. LodeStar – I think we’ve covered all the questions we had. It’s been great visiting your shop, here in South San Francisco. Gus – Thank you LodeStar – You moved here from Burlingame, right near the San Francisco airport. You’re definitely in the high rent district now. Gus – Well, I bought this place when we moved here in 1993, so we don’t have to worry about that. LodeStar – So, someday you’ll sell this for a hotel and…. Gus – (Laughs).

TECHNO-CLASSICA AND TECHNORAMA M-100 GROUP 2004 European Tour All M-100 Members are eligible to join a 2004 European Driving Tour that will include the two most popular vintage car events in Europe , TechnoRama, Kassel, March 27 -29 and TechnoClassica at Essen, April 1 - 4, 2004. John Olson, who has hosted a half dozen similar tours in the past, is preparing an itinerary that also includes few days with rented SLs on the famous Romantic Road through German’s oldest walled villages, a night in a 500 year old castle on the Rhine, and of course, several days of red carpet treatment visiting AMG, Mercedes factories and museum and the Classic Center. There will even be time for the Sinsheim Auto/Plane/Military Museum and a quick drive to France to see the former Schlumpf Museum if there is interest. Pencil off March 26 through April 8, 2004 and phone John Olson (612-377-0155) for more details. Exact pricing is still being researched, but count on a memorable trip with like-minded travelers that still allows a personalized itinerary. By renting cars our daily routes can vary with rendezvous for some evening dinners, lodging and optional destinations.