TheSamba.com :: View topic - Please help me logicalize this fuel problem

Tue Nov 18, 2008 7:21 am

Background:

I'm awaiting a new FPR and 2 new injectors (to finish a set) from BusDepot. I know that the FPR is allowing the pressure at idle to be too high. The acceleration pulses a little too. This is probably both the pressure and the 2 injectors. The PO only had the square white filter before the pump. I cut it open and it was full of chunks. I now have both filters. Pump makes a slight hum sometimes even with the new pre-pump filter but, it puts out adequate pressure.

Here's my issue:

When starting from a stop on a hill, it is very difficult to get the van to go. Let me clarify that a bit. When the clutch is released, I can pump the accelerator pedal up and down to the floor with very little response (close to no response). It is as if it just isn't getting any fuel. However, starting off from a flat or downhill stop is fine. The van also powers up the same, and any other hills, so long as the van is moving first.

This seems to be a fuel delivery issue but, there are times that I put as much load on the engine by going up a hill while moving and the engine is able to get adequate fuel. I would assume that maintaining the fuel pressure would, theoretically, have to work its hardest when the van is on a downhill. Starting on a downhill obviously puts less load on the engine though and requires very little fuel. But, why would the van have THIS much trouble starting out on a hill? I'd assume the fuel pressure would be high anyway (remember the FPR), and that the system isn't struggling to deliver fuel.

I'd really like to get some ideas as to how this would be happening. I'm hoping that the new FPR will fix it but, I'd like to know why if it does. If it doesn't, I'd like to have a theory as to what it going on. I have not had someone sit back there with a fuel pressure gauge while it happens because my brand new gauge leaks a bit. If I can't get a handle on this logically, I will try harder to get the fuel pressure gauge to stop leaking and give that a shot.

Tue Nov 18, 2008 8:14 am

If you found shit in the filter I'd have to start with the tank, and I also won't put any new fuel parts on till you can verify the tank is clean.
If you found chunks in the filter, you don't know what might have gotten by.
Did you find chunks of rusty metal or like rocks or debris in the filter?
how long has the new filter been on?
Do you know if the van was left sitting unused for any lenth of time in its past, like several years?

Tue Nov 18, 2008 9:12 am

Is it the same tank full or empty? I worked on a beetle convertible under warranty years ago. It would quit going around a corner. Die, restart and be fine. There was a bead of solder that would roll past the tank outlet and get sucked closed. The engine would die and the solder blob would roll away. If the problem is better with a full tank, could the suction and return lines have been swapped? I don't recall how the tanks are plumbed.

Tue Nov 18, 2008 10:46 am

Good questions. I am putting new fuel system parts on but, only because I am running both filters and will change the filters often until I am able to replace the tank. The new front front filter was put in place when I added the initial 2 new injectors. I'm not sure how long it had been operated with the pre-pump filter only. I'll be sending the old injectors off for reconditioning. The tank is probably very rust stricken. I'm sure that debris is the reason that the FPR and the injectors need replacing. The pieces in the filter ranged up to to just smaller than pea gravel size and resembled rocks.

I've thought about the rust over the tank outlet on hills but, it occasionally does this on flat ground too...just not every time (it seems to be dependent on the duration of the stop time). It does not happen only when the tank is empty nor does it happen while already moving up long hills (doesn't have any trouble at all). Most of the signs seem to point to something with the FPR. It is very possible that it has debris in it. I'm not sure how it operates internally to know if it could cause this issue.

Tue Nov 18, 2008 11:46 am

What will damage a fuel system is the small stuff that gets past the filters. You are lucky because I have seen newreplacement fuel tanks for the vanagons. On my 68 I had to buy a used tank. The fuel pump is your supply or volume. Without the regulator, the fuel would circulate back to the tank and the system would have no fuel pressure. The regulator is a restriction on the return to the tank. This restriction creates your system pressure. To diagnose the pressure regulator as the culprit, you would need to run the van with a fuel pressure gauge attached and watch the pressure as your engine exhibits the problem. If the regulator stuck open, pressure would drop below what the injectors are expecting and the engine would miss, stumble, and die. If the regulator stuck shut, the fuel pressure would go to the max, the engine would run super rich, stumble and die. I think you should invest in a pressure gauge to do some testing and at least drop the tank and look inside.

Tue Nov 18, 2008 11:58 am

Here's a thread with a discussion of FPR function. On the second page is a description of how it works:

http://www.thesamba.com/vw/forum/viewtopic.php?t=204445&highlight=diaphragm

Tue Nov 18, 2008 3:00 pm

rsxsr wrote: To diagnose the pressure regulator as the culprit, you would need to run the van with a fuel pressure gauge attached and watch the pressure as your engine exhibits the problem.

I guess I'll have to do that. My gauge just doesn't have a long enough hose so, I'll grab a longer hose and see if I can place legitimate blame on the FPR. Thanks for the link Tencent. I'll read up on it.

Tue Nov 18, 2008 9:54 pm

hansh wrote: rsxsr wrote: To diagnose the pressure regulator as the culprit, you would need to run the van with a fuel pressure gauge attached and watch the pressure as your engine exhibits the problem.

I guess I'll have to do that. My gauge just doesn't have a long enough hose so, I'll grab a longer hose and see if I can place legitimate blame on the FPR. Thanks for the link Tencent. I'll read up on it.
:D :D :D Good luck on your fuel problem Hansh! I just could not resist as I always try to learn something new every day, so I went to dictionary.com as I thought you were teaching me a new word... :D :D

No results found for logicalize:
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I know you will probably slap me when we finally meet, but, I just could not resist! :wink: :wink: :wink:

Tue Nov 18, 2008 10:06 pm

Hey carterzest that word is listed in the same dictionary that Bush got his famous " STRATEGERY " in.
Thats the same dictionary that Professor Irwin Cory authored. #-o

Tue Nov 18, 2008 11:50 pm

carterzest wrote: learn something new every day, so I went to dictionary.com as I thought you were teaching me a new word... :D :D

Only people who don't have enough knowitude use things like dictionaries. Language is a tremendously dynamic component of our society and changes faster than it can be tracked. So, how do you know that I'm not just that far ahead of the curve?

Wed Nov 19, 2008 12:51 am

hansh wrote: carterzest wrote: learn something new every day, so I went to dictionary.com as I thought you were teaching me a new word... :D :D

Only people who don't have enough knowitude use things like dictionaries. Language is a tremendously dynamic component of our society and changes faster than it can be tracked. So, how do you know that I'm not just that far ahead of the curve?

Meh...... :D :D :D

http://www.chicagotribune.com/news/nationworld/sns-ap-eu-britain-new-word,0,1807854.story

I mean if Simpsonsglese can make it to the Dictionary, you may have one over on me! :lol:

Wed Nov 19, 2008 5:31 am

Enough, Already. Even a meathead like myself knew what he meant. My big question is: where do I get this "pimp oil " stuff? No doubt TK will straighten this out for me.
Al