Ive been getting to the bottom of my fuel delivery problems. Slowly but steadily when time allows. There was considerable air getting in the system likely from the fuel filter bolt o rings, since replacing them and the hand primer pump, its managed to start again and run with less problems.

I purchased a Mityvac, well worth it as it gave me an Idea of where the air was getting in and could isolate the problem quicker. There seems to be some air still getting in from somewhere around the fuel filter. Ive noticed with the handy gauge on the Mityvac it shows vacuum/pressure/resistance of about 2 or 3 in.Hg (or 5 kpa). very little anyways. but when I hook up the mity vac to the line that exits the primer pump assembly, before entering the IP (I think?) the resistance increases considerably.

Fuel wont start flowing when I pump it until the needle reaches 5 or 6 in.Hg (or about 17 or 18 kpa) is this normal? and if not could there be an easily remedied problem in the primer pump assembly like a stuck valve or something. I replaced the hand primer pump with a new one as the old one was definitely leaking fuel, however in a series of primer pump changes by the mechanics they put the old one on and left out the copper washer, and I tossed the old one. a new one is on order but in the meantime the car has run without it. Is the pump assembly easy enough to remove?

I have same as the one on the right. It looks as if I may simply have to loosen the large bolt in front of it? On pictures of new ones on parts ordering websites it shows the opposite side with 3 holes and a gasket. Are these holes for a bolt or an allen wrench? I cant see without taking all the hoses and parts off. Any suggestions as to how to go about doing this and/or if the resistance the pump seems to be causing is normal?

I'm in the same boat

elaborate on your setup and which lines you attached to.

perhaps, but unlikely. Fastlane sells a full rebuild kit for this pump.

the entire pump comes off with three nuts around the perimeter of the base.
no, not unless you are prepared to rebuild the pump.

Do some searching / research on fuel pressure. There's alot of good info here.

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I attached the mityvac hose to the line that exits the primer pump assembly (transparent brown line) and pumped (sucked) with the mityvac. It has various attachments to stick into varying hoses. at present the transparent line (the one on the left of the assembly in picture above) is actually spliced with a section of rubber fuel line for whatever reason. I think the mechanics who installed our greasecar veg oil system did that. It loops up then down again to another banjo bolt on the IP. So what I did is simply undo one side of the rubber fuel line and sucked with the mityvac. so the fuel is coming directly from the primer pump assembly. Not through the IP
or anything else.

I dont think we have fastlanes here up in Canada. Napa perhaps? And do you mean 'perhaps but unlikely' that its a stuck valve? or that the resistance is normal? Is it a complicated part to take apart and reassemble? (i.e little springs firing out everywhere or something)

Great, so do I need to remove all the lines and the primer pump to access the 3 bolts? and do you think the problem would be anymore diagnisoble by a visual inspection by removing it?

Thanks Ill do that

I cannot answer the question regarding pressure differences. The info is there if you search and infer. Search "pressure relief valve"

also, I am not aware of a fuel line that goes to the IP after the primer.. the lift pump / primer pump leads to the filter, the filter leads to the IP.
Fastlane is the retailer for this website only, not a chain of stores.
it might be a little easier, but is by no means necessary to remove the lines. There is one nut on top, and two below the hand primer. A bit of oil will drip from the IP once you remove this pump from the IP housing.

a visual inspection will not tell you much with this pump. Buy the rebuild kit if you eliminate other variables first. There is no reason to pull this pump unless to bench test or rebuild.

I would suggest inspecting all your lines and connections before testing this pump.


As a general rule, it seems to me that these systems add an incredible amount of chaos to a very simple system. Hunting them down requires a very systematic approach.

In a perfect world, you would replace the soft metallic crush washers on each side of a banjo bolt after each disassembly.

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I meant that it was unlikely there was a stuck valve. You can see the 2 black, plastic plungers here. They are the closest thing to a 'valve' in this assembly.

If air is getting into your lift pump and you are positive the leak is through your pump... it past one of those copper washers. Anything else is a hose.

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Comment on the vacuum needed to move the Fuel.
I have no specific spec as this is sort of new territory for someone to investigate

However, the Fuel has a certain amount of weight (pulling the fuel up against gravity) as well as viscosity to it. Added to this is some resistance due to the long hoses and tubings going to the Fuel Tank.

The 5-6 Hgs does not seem unresonable when you think of the above.

If you hooked up the Mighty Vac at the Fuel Oulet of the Fuel Supply Pump; besides the stuff mentioned above you also have to create enough vacuum to overcome the pressure of the 2 little valve springs.

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84 300D, 82 Volvo 244Gl Diesel

Thats a great Shot, just what Ive been looking for! Thanks.

I see the little plungers, so one would open up while the other closes when you push down on the primer pump, and then the other would open and close when you release it, essentially a one way valve, allowing the fuel to pass only one way all the time. It appears because there is the extra resistance comming from the primer pump, vacuum preassure builds in the lines and wherever the weakest seal is it lets in the air. I wonder if perhaps the amount of resistance is whats really causing air to get into the lines because somethings got to give somewhere if enough preassure is built would it not? However if this resitance is normal then yes I definately have to keep working out the leaky lines.

Whats the big spring in the center for?

the pump you are looking at is both the hand primer and the fuel supply to the IP. When the car is running, a camshaft in the IP is turning and pumping the lift pump.

The big spring is the return for that metal piston you see right next to it. You could call that lift pump piston.... I guess.

edit*
ps - thanks for inspiring me to do this. Ive been putting it off. Please update your final conclusion if you ever figure this out.. I have very similar issues but only when the tank is low.

It might help to make a mental record of the conditions that are co-morbid with your fueling issues. (temp, fuel level, load.. etc..)

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this might help illustrate the interior workings of the lift pump and its marriage to the IP.

See the roller bearing? That moves in and out of the housing and pushing on that metal piston. The piston is highly machined as is the cylinder it resides in.

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Heres a picture of the line coming from the primer pump to what looks to me to be the side of the IP. Its an older picture with the old style pump as you can see, It could be because the veg oil kit installed needed to have things routed a bit differently to keep supply/return lines separated to avoid cross contamination of the filters. Not sure though, Im still learning about how all this works. And I find it very interesting. but I wouldnt find it too surprising if the mechanics who installed the kit did something wrong.
In the picture if you look closely you can follow the line that leaves the primer pump up and through the cluster of lines then down again to end up at the banjo bolt that looks just above bolt on the primer pump. would this not be going into the IP?

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wonderful.

You are no longer 'stock' by any means. If it was me... I would make some diagrams showing me where my fuel system was pressurized vs. vacuum. Air will only enter on the vacuum section. trace your diagram one section at a time and make markings on sections that have been completed.

- I would inspect all the banjo bolt washers.. they were probably reused.
- all those questionable rubber hoses clamped onto the shiny plastic stock fuel lines (no comment on whether that is a legitimate install)


this is the stock setup:
Lift pump goes to one of those banjos on the filter housing (engine side), while the one right next to it goes to the IP.

Your setup begs the question: "is my filter under pressure, or under vacuum?"

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That could be very good information to have. It would rule out a problem with the primer pump assembly. Looking at the picture, I'm trying to see how the springs would be mounted in relation to the plunger/valves. Are they oriented in teh picture the same way they would be installed and working?

So both of them would be closed unless theres fuel being pushed/pulled through? And are these little plungers rubber or plastic or are they metal? (i.e. wondering how well they would seal)

I have a schematic form Greasecar here that shows the fuel line redirecting needed in order to accomodate the switching of fuels. Im a little suspicious that veg oil is still getting in the diesel fuel filter as it smells like it and feels like it when I remove it. They said teh setup is such that there wouldnt be any cross contamination though. However when I see the main return line, it has to go through the Diesel filter regardless of what kind of fuel is being used at the time. does it not look like that according to this schematic?

I can see some of the aluminum washers are crushed at an angle, even though it looks like its making a seal. I was trying to find a schematic of these parts so I can find the part number for these exact washers but so far I haveent come accross one that can gibve the exact part number or something that I can cross reference it with.

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Michael,
I am replying to your thread to keep the info together and keep the information public.
I believe you want to contact a Bosch certified injection shop, or any shop that has a strong alliance with Bosch. As long as you have the number from the side of your pump, they can get you any part you need. I would not waste my time with the dealer, they are more interested in newer cars.
I have some used spares that I can measure for you with vernier calipers, but the measurements will be slightly off b/c of the deformation issue- Still good numbers though.

If you really have ZERO luck getting a new washer... you can reform your current one. (I know... I know...) Place it b/w two strong, flat surfaces and beat them flat with a hammer. Then polish your washer with light sandpaper, finishing with steel wool. If the copper appears to be completely removed, you should definitely find a new washer somehow b/c of the corrosion issues involved.

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for whatever its worth:

I cleaned the areas around the threaded inserts.

Loosened each one 1/2 a turn, then tightened each one as best as I could.

I now have the smallest bubble I have ever witnessed in the clear prefilter and my tank is low. I did not replace any of the washers.

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