boxer CIS fuel system inspection / repair

Well I decided to finally sort out some issues with the boxer CIS. Ill have to keep adding pics as I go along since I just started today and I have a long way to go. So, I started at the tanks and ill work my way through the system and reapir or adjust as needed rather than rebuild everything in sight. As long as Ive had the car its had a hot start issue that Ive lived with because it was minor and I could tollerate it until now. Enough is enough. My car is fairly original, it has the original style Mercedes fuel pumps and steel injectors, time for some updating of parts.

The first thing I did this morning is remove the drivers side pump for inspection. It was simple and done with a few hand tools that everyone should have even if they just have the factory tool kit. The pump, accumulator and filter come off as an assembly then you can remove the pump or accumulator at that time. The filter itself can be replaced without removing the entire unit which makes sense. If your accumulators leak then remove the whole unit and deal with it on the bench, very easy to do. Since im starting from the tanks up, I have to remove the fitting in the tank (now that the pump is out of the way) that feeds and strains the fuel that enters the pump which then goes to the main filter prior to entering the fuel distributors. Dave Bendl showed me some nasty pics of his tank screens which has prompted me to do the same. Part of me is hoping I find something bad so it feels more satisfying that I went through everything but at the same time I dont feel like buying a truck load of parts either. Unfortunately I dont have the right sized socket here to remove the strainer but tomorrow ill pick up a cheapie socket and keep it for home use...Dave, do you know the size of the socket I need for the strainer. The pump is in the middle of the assembly, the accumulator is the greenie coloured thingy with the 90 degree bent line going to nowhere. If your accumlators leak fuel they will leak it out of that free line onto the ground. Just remember all injected boxers have 2 of everything so the other side has this same assembly there too.

So off came the pump once I removed the hard line from the pump the I loosened the gear clamp on the rubber supply hose from the tank to the pump. There are 3 10mm head nylock nuts holding the unit onto the frame and finally the 1 positive wire to the pumps, presto its out. I seperated the line from the pump to the accumulator once off the car then looked inside the pump at the check valve. I cant get at it, the buggers made it in such a way you cant do much with it. Ill soak it in fuel injection cleaner but I bet I wont have much luck fixing it. The purpose of the check valve it to retain rest pressure once the car is shut off preventing the fuel from returning to the tank. If this happens the car has to prime the system all over again but its more difficult on a CIS car since the injectors wont open to bleed the air out and let the fuel spray in, they need the fuel pressure to open them but it aint there. This leads to a long crank period......dreadfuly long then it starts to sputter a bit and finally start running on 5 cylinders, 6.....10, 11 then 12 which isnt the best situation when bystanders are watching eagerly to hear the car roar to life. Very frustrating and makes for a red face. On the plus side when the car is cold the cold start injectors (which are electro-magnetic injectors similar to a late model injected car) fill in by supplying the fuel to the engine masking the problem of not having fuel spraying out of the CIS injectors right off the bat. Once they come on-line the engine runs better. When the car is hot, you`re screwed, no fuel.

Removing the pump for inspection and the hose from the tank to the pump is as far as Ive gotten today, ill see if I can yank the fitting out of the tank tomorrow. Oh, I drained the fuel from the cross-over pipe first. The gauge read empty, right on the line red light a glowing. So I figure hey, a 4 liter washer fluid jug should cut it - Doh! 6 jugs later the empty tanks were truely empty, fuel up to my armpit and all over the floor, lol it was exciting and im not as worried about running that low and looking for a gas station!
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Thanks Dave,

Yesterday I took one of the pumps apart since I wanted to see what exactly was wrong with it. Either way I had to replace them so I had nothing to lose. Turns out the glue that they use on the windings had started to break down and bits had come off lodging themselves in the check valve. So, new pumps are in order, ill show pics later.

 

The pick is pointing to the small black ball which is the check valve. You can also see the epoxy on the windings which was the source of the debris that jammed the check valve off its seat. No avoiding that happening. Just waiting for the new pumps then onto more photos as I go through the system and follow it up with a gas analyzer with more pics of that proceedure as well. Ill have the car dynoed again and post the results.
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I didnt try to find the originals, I figured the better pump is the upgraded one anyway. As far as being correct, its pretty minor, at least its still a bosch. I was thinking, if I did find an original how long would it last before the epoxy stars breaking down on the windings? i doubt I would get another 25 years out of the NOS ones. Whats your take on it?

 

The 25 year thing assumed some use from me for several years as well, lol, not just on the shelf! Yes the coversion is simple and the pics will be up as soon as I get the parts.

 

The pumps came today via UPS so here they are! Ill take a pump to a local hydraulic place to get the right banjo fitting for the pump outlet. This is the only mod required to make the updated pumps work on the boxer....as well as 308s with the CIS. The original line has a compression fitting on the outlet that loops over to the accumulator so Ill fabricate a new line using the new banjo fitting. I bought the pumps from Autohaus Arizona - fantastic place to deal with. They sent the copper washers and cap nuts for the banjo fittings. I should have asked for the banjo fittings from them, they probably had them so I goofed up there. Ill update with more pics as I go along then move to the injectors, etc and tuning.....

The reason for the updated pumps needing the line change is the move to the servicable check valve located in the outlet of the pump. You can see the gold cad fitting that unscrews from the new pump. Thats the valve that causes the grief, the original pump doesnt have the external valve.
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The fuel lines and fittings came in today from Larry Fletcher - thanks Larry! So now I can move forward with all the needed parts. I mounted the pump today but ill have to play with its position once I make the new line from the outlet to the accumulator. Part of me likes the original line with its smooth bends vs the 90 degree of the banjo setup but I cant see making it much better due to the banjo design on the end of the pump (maybe you engineer guys out there can chime in). I just like things to be better than they have to be and without studying flow rates between the 2 line designs I can only assume it flow less but still more than enough for the 2.5 litres of engine being fed per bank. Ill make a tool (block of wood) to install the plastic line on the fittings which is the same technique us injected guys get to deal with when the injector lines start leaking (like one of mine did 2 years ago). Its simple just hard on the fingers.
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Nice explanation Steve.

The accumulator fitting can be rotated anywhere I like. Its the same style fitting on both ends from new so the new pump means we have to replace at least the pump end of the line, Ill change the whole line and keep the original uncut. The replacement fitting for the accumulator end of the line is identical (in how it seals) except for the inlet angle being 90 degrees rather than straight on so no adapters are needed there. A simple line with a banjo on one end and the stock style fitting (with a 90) on the other gets it done. I plan to arch the line upward from the pump slightly then back down to the accumulator instead of straight across. I cut up a wooden block today and im going to drill a hole through it slightly smaller than the plastic line to act as a holding tool so I can push or drive the new barbed ends into it. Ill post pics of that as well. The proceedure is the same for the injector lines just smaller hoses.

 

The check valve was held open by a piece of debris from inside the original pump motor. If I were successful at back flushing the old pump to dislodge the debris it would only happen again later down the road since its the disintegrating epoxy on the motor windings that held the checkball unseated in the first place. It would be a good cheap quick fix for one who was selling the car and didnt want to spend the dough / time to do it right. And yes, it was the cause of the hard hot start for sure.

 

I made the new line a few minutes ago, took about 15 minutes and some elbow grease to push the barbed ends in by hand. The wooden block is key or you'll fight with the line and need a stiff drink afterwards. I know this from doing my number 12 injector line a couple of years ago. Off topic slightly......every time I run my boxer I look at the injector lines, run my hands along the underside of them feeling for wet fuel, that how I discovered by leaking injector line. Its something that we CIS owners should consider doing before and after a blast just to be safe. This pump is ready to go but before I do that im yanking the tank screen fittings to have a peak, ill post pics of the outcome then the other side needs to be done.
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I yanked the fuel pump pick-up tubes from both tanks today along with the right side pump and found the socks on the pickups are toast. They are crispy and break when pressed on so they gotta be changed to protect the new pumps. Anyone got some they can sell me? Ill call ferrari monday I guess as well ill send the pickup tubes out for plating at the nearby alternator rebuilder, he sends pulleys out all the time by the bucket-load with a quick turn-around. Both steel pick-up tubes are corroded, the gold cad plating is long gone so it looks like I have barnicles on the insides and outsides of the tubes - not good. Blast them and plate them like new and im good for 25 more years...maybe. You can see the layout of the fuel supply system in the boxer, Ill replace the right side pump too making another line to adapt it then once thats all back together ill move up to the injectors - cant wait to hear this thing run again.
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checked ferrari stock on the pick-up tubes - NLA, number changes up to another NLA part yippee! Guess Ill be using a generic sock. Bet im not the only BBi owner that needs these.........

I made the line for the other pump so they're ready to go back in once the sock issue is sorted out. The pumps are in the way of the pickups so they wait on the shelf until the socks are back in the tanks.

 

I was considering an inline filter upstream from the pump but thought if I can get some socks instead ill go that route. Adding a filter in that tight spot is a PITA. Ill keep it in mind but see what I can find sock-wise first then make up my decision.

 

I couldnt just sit around and pick my nose today so I moved a bunch of things around and lowered the boxer to pull the injectors. As expected I need to replace the o-rings for the injectors. Now that I have them out I can take them to the local Mercedes dealer and match them up tomorrow morning. The injectors simply pull out. I chose to remove 3 at a time lines in tact then disconnect the lines on the bench. Getting the 12mm wrench on the injector with the line on proved to be difficult and the injector nuts were very tight. These are most likely the original injectors being they are steel, look old and the car has 35K on it.
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Thanks Dave, ill see what I can get up here. Did you use that nylon zip-tie in the end? I figured a steel clamp of some sort would live longer in the fuel.