injector pump losing prime?

[therast]

I have a 91 jetta gl non turbo and i purchased the car a month ago. I have had 11 vw diesels. In the last month I have driven the car about 4500 miles to Canada and back. Yesterday when i attempted to start it it took literally 2 minutes for the pump to draw the fuel up and then the car started and putted and then ran and I drove it to work. After 11 hours of work it did the same thing. This injector pump is slightly different than ones on my previous cars. It has a "pod" on top with vacumn lines going to it and then run to the passenger fender well where there is some sort of valve with one vacumn line and one wire. what is that stuff? Please advise am i looking at a pump rebuild or is there something else possible?

[KubotaPowered]

Sounds like you have a slight leak somewhere thats allowing air to get in when its shut down.

[HIGH PSI]

The 'pod' on top of the pump is a fuel enrichment diaphragm. It limits fuel when you are pulling out to prevent smoke and then uses a vacuum signal to give you more fuel once you are at higher RPM's.

It does sound like you are getting air in your system. Have you done any work to the car lately, fuel filter perhaps. Sometimes a new filter won't always seal up properly. Also look for a puddle under the front of the engine. When the pump drive seal goes bad it can drain the fuel down out of the pump. Check all your fuel line connections and make sure they are tight. Perhaps changing the washers on the banjo bolts would be a good idea. Do you have any fuel around the throttle shaft of the pump? That is another common place I see air getting in. If there is nothing obvious sometimes putting a check valve in the line between the filter and the pump prevents the fuel from being able to drain back into the tank. It is ideal to fix the problem right if possible though, rather than just using a valve as a band-aid.

[therast]

Joel thanx for the info. I bought this car about 6 weeks ago and have not made any adjustments or repairs to the fuel system I have driven the car about 4500 miles and now the car will leak down in about 10 hours. What else can you tell me about the fuel inrichment pod and what publications could i read concerning it. I don't see any leaking fuel and I haven't touched the fuel system at all actually all of the banjo connections are tight because i tried shaking them all. Any other suggestions? Where can i get the proper timing setting for this year and this pump if I have to change pumps. Rast

[fukengruven1982]

theres a check valve somewhere on you line between the tank and the injection pump...only allows flow one way....could be bad like my old 1.6....its a really cheap fix..cant hurt to try it...fuel is probably draining back to the water seperator /tank just a thought..

[dsl_lvr]

Old post but maybe someone will reply.

Anyone know the exact location of the check-valve to which fukengruven1982 refers? I don't recall ever seeing a checkvalve in the system. Mine is a '91 also, if that matters.

If a check-valve exists, I probably have a piece of coagualted bio-fuel in it, keeping it from seating. I got some bad bio last year and plugged up my fuel pick-up screen ans well as the fuel filter. My curreent problems are probably an aftermath of that.

[pdjetta]

I have had the loss of prime issue in a 1.6 VW diesel and it was a failed injection pump main seal. They rot after many years. You might want to check this. The timing belt and injection pump sprocket must be removed to replace the seal. I was swapping engines and had the pump removed when I replaced its seal. You may be able to replace the seal with the pump isnalled on the engine.

--Nate

[dsl_lvr]

thanx but pump was re-sealed about 10,000 miles ago and there is no exteranl sign of leakage anywhere. I did have an injector return line seeping but I replaced it. Fuel filter is new and I can suck fuel through it easily so that isn't source of starvation. Besides, it only happens when it sets overnight. Incidentally, this is an itermittant problem. That is the most odd and frustrating thing.....

[ToddA1]

Since its only an overnight thing, are you sure it's not glow plug related? Are you physically repriming the car to get it to start?

-Todd

[Tinker Toy]

One of my old Parts Place Inc catalogs had a short writeup about losing inj pump prime due to a failed rotary shaft seal as was mentioned. That can happen due to the cam belt run too tight for too long that wears the shaft bearing egg shaped that causes the seal to fail. The only permanent fix is a new pump housing or a new pump as there is no bearing insert; the housing material is the bearing. A possible workaround is a very low pressure electric inline pump that will prime the inj pump. if I did this, I would use the electric pump momentarily, long enough to get the engine started.

I have been running my cam belt for many years and miles with a very slight lack of tension and the pump is still ok; no leaks. I have used a quart of biodiesel with every tank fill since the change to ULSD several years ago. Possibly these are good things to do as my inj pump is original and has never been resealed.

[ToddA1]

That doesn't make sence ... the mainshaft bushing is still available. Unless the wear is so great that it actually wears into the AL housing, I can't see it being an issue.

-Todd

[Tinker Toy]

Ok, a question has been revealed here. Does a VW inj pump have a rotary shaft replaceable bushing or not? Is there a difference between IDI and TDI versions? Expert assistance is needed.

[ToddA1]

Yes and yes.

-Todd