Hi all, I'm having serious fuel pressure problems. It all started when my car had difficult cold starts (had to turn key during several seconds and then it would first start a few seconds on 3 cylinders and run fine after). Because of this small problem I started measuring control and system pressure with the known pressure gauge setup. First I had the following results: -cold control pressure was too high according to the ambient temps. at that time - And system pressure was 4,7bar which is the minimum. Some time later I did some new pressure tests and now the gauge doesn't move when checking cold control pressure (valve open) and only goes to about 3 bar when checking system pressure (valve closed). I also have to push the throttle a bit to start it. When I go off the throttle it stalls. When the car is hot and I go off throttle very gently it idles on 4 cylinders but poorly. Rest pressures goes down a bit after time but doesn't plunge. I can't check if it falls too much acc. to spec. or not because my pressures ar too low to start with. What I've checked: - Control plunger inside fuel distributor is not sticking - no leaks at pump or accumulator (all is dry) - fuel pump clearly running (zooming) - cold start injector sprays perfectly and doesn't leak - main fuel injectors have an acceptable spray and don't leak - WUR resistance is 22 Ohms, which is good. - system pressure regulator in fuel distr. looks brand new. I've replaced the fuel filter 4 years ago but the car only ran about 3000 miles since than. Could it be that the fuel is pumping but is immediately being returned back to the tank instead of building up. Because I have almost no pressure, unless I close the valve in the WUR line. I don't think it's the accumulator cause it's function is to maintain pressure in the fuel system after the engine has been switched off. Important point: fuel distr. is sweating a tiny bit on the side, but this has been the case for a long time and the car Always ran fine. This can't stop the pressure frm building up and would only affect rest pressure right? Any help would be appreciated guys !!
What car ? All related perhaps ? ... Same side isn`t it ? Maybe the spring in the regulator has weakened ? Can you disconnect the return line and check ? If a Mk2 ... lift pump `gone` Cabling to pumps breaking down ?
if system pressure test only gets you 3 bar then i would suggest you have a faulty fuel pressure regulator, weak fuel pump or a leak in the supply side of the system. the accumualtor wont affect the pressure readings unless the diaphragm has split inside but then if it was leaking enough to loose you 2 bar of pressure i would expect to see fuel coming out of it pretty fast! take the pressure regulator out the metering head and check the condition of the o'rings, replace if squashed. The part number for the full valve is 035198685 it's NLA but you can still find it aftermarket, this is quite expensive as it includes the valve itself, a kit of shims plus the o'rings. In the kit of parts are 2x o'rings 3.2mm x 2.25mm and 3.9 x 1.8mm, one of these is the smaller one at the end but unclear which. The larger one is something like 7mm x 2mm You can get just a seal kit 035198691 which includes the o'rings above plus a new copper washer to seal the valve into the metering head
Sorry, totally forgot to mention what car: '88 Golf MK2 GTI 16V (KR), all original. @jamesa: what do you mean same side? If you mean if the leak is at the same side of the system pressure regulator, answer is no, it's on the opposite side of the distributor. Why do I have to disconnect the return line? How do I check if thhe pick up pump is failing? @ rubjohnny: As mentioned, the system pressure regulator in the fuel distributor is brand new and original. I'll re-check again when I get home and make a picture. I also thought about a leak somewhere, but couldn't find anything and it seems the leak would have to be big to lose 2 bars of pressure. How can I check the main pump power or flow rate ?
for voltage tests disconnect the main pump plug and pop in a multimeter across the terminals, then switch the ignition on and check the reading. Then for flow test disconnect the pump feed from metering head and point into a bucket then measure the amount of fuel delivered for exactly 30 seconds compared to this graph:
I checked the flow rate of the main fuel pump. According to the Autodata manual the KR/PL pump should deliver at least 1,5L/min. I had to stop after about 15 seconds because my 1L bottle was almost full. So the pump is alive and kicking. I gues this logically means the problem is somewhere between the fuel distributor and the return line to the tank? I'm starting to think that the fuel pressure gauge is already faulty cause it doesn't make sense and the gauge is low quality (https://www.vidaxl.nl/benzine-injectie-systeem-tester-70-delig).. I'll take out the system pressure regulator again tomorrow.
have a look at the banjo bolts on the inlet pipe of the metering head, they arnt the filter type are they? these should have been replaced as one of the early service schedules with plain bolts
Hmm didn't know there were banjos with filters in some metering heads. The metering head is from '89, that I'm sure. You have a picture of such banjos? When you say inlet pipe, do you mean the big banjo on the line coming from the fuel pump/tank?
yep thats the one, I dont have a picture but if you look inside the bolt you'll see it if its there cant miss it. long shot really though! check em both just in case but im pretty sure it was only on the inlet bolt
I've checked the system pressure regulator again, O-rings are perfect, spring is perfect, holes are free, piston is spotless, .. And indeed, the inlet banjo had a fine mesh filter in it, which was also spotless. I'm expecting an old but original VAG 1318 gauge/valve soon,bought it online. So I hope to be able to do a trustfull pressure measurment soon. I've noticed that when I undo a bolt there's no pressure on the lines (the day after I activated the fuel pump for example), so I think I have no rest pressure. Could it be the main pump check valve ?
is the usual suspect if residual pressure not maintained, you should see at least 2.6 bar after 10 minutes. overnight id not be worried if pressure has died off completely. accumulator could be a cause if its holed inside, to check for that take the wee screw out the back of it and see if any petrol comes out
Thanks for the tips, I'll check the bolt ! On Monday I should receive the VAG gauge so I can do a new pressure test.
Update: I've did a pressure test with a genuine VAG1318 gauge kit. Everything seems fine. cold control pressure (15C ambient): 1,25 bar hot control pressure: 3,6 bar system pressure: 5 bar holding pressure: 2,6bar (10min.) / 2,45 bar (20min.) For a cold start some light throttle is needed. Hot start after 20min. rest was no problem. Idle is fine. Could it be an electrical issue? Ignition coil or ignition wires? Spark plugs are almost new.
Have you checked ISV?, think it should be wide open when starting (hence why it starts with a little throttle).
hmm, good idea, i'll check it when I come home from work. Hope it isn't the ISV, these are expensive as hell if I'm correct.
