GTi DX low control and system fuel pressure
Posted
#1660638
(In Topic #236350)
Newbie
I have an 86 GTi cabby with a DX engine, it will run for around 5 minutes and then misfire and stall.
I have checked fuel pressure and the control pressure doesn't even register on the gauge. When closing off the supply to the WUR I can get the pressure up to 2.5 bar. Opening the tap back up and the pressure starts to drop.
Things I have checked/replaced
In tank lift pump, fuel pipes, filter and earth wire.
High pressure fuel pump and pipes.
Accumulator
Fuel filter
Spark plugs, HT leads, coil, dizzy cap.
Purged lines into a cup no dirt.
There are no fuel leaks that I can see
Checking pressure at the filter and I chickened out at 6 bar.
Pressure relief valve removed and all o rings are still round and look like new.
WUR opened, no leaks, bimetallic strip bends when 12 volts applied, reassembled and no difference to running or pressure.
Removed metering head feed line and no gauze filter present.
Timing checked with a strobe at 6 degrees BTDC
Might be something I've forgotten but any help will be appreciated.
Thanks
Rich
1986 Mk1 Golf GTI Cabriolet
Posted
Settled In
With mine from cold it would run for a few minutes then revs would drop right down to the point it would keep stalling until it had warmed up a bit, though don't recall it misfiring. Turned out the auxiliary air valve wasn't working properly. Something still isn't right now but it it is better after a good clean out and doesn't cut out
Posted
Newbie
I think the AAV is working as the engine revs high for a few minutes then calms down to around 1000rpm. A few minutes later the misfire starts.
I think everything points to the WUR but I can't find anything wrong with it. I have ordered another one, no guarantees it will be any better but worth a try.
I'm wondering if there is anything else that can affect control fuel pressure.
1986 Mk1 Golf GTI Cabriolet
Posted
Settled In
Can test AAV in situ by squeezing hose to it, when cold revs drop when warm shouldn't make any difference.
Did you order a second hand or refurbished WUR? You can get a rebuild kit for them off ebay for around £34 which I will try at some point as I think my issue is WUR or wiring to AAV, perhaps both. But need want to get ignition timing And mixture checked/set first.
https://www.ebay.co.uk/itm/184451697447?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=VBNcl3M6S-K&sssrc=2349624&ssuid=ywyXn1ORRP-&widget_ver=artemis&media=COP
Posted
Newbie
I was looking at those rebuild kits but then saw a second hand WUR and AAV on eBay for not much cash. If that doesn't work I think I'll try the rebuild kit. I've also seen one for the metering head which might help.
That's on my list as well to send it somewhere for fuel mixture. My only worry is I could be adjusting the mixture to hide another problem.
If you're near sheffield you can always borrow my timing light and pressure test kit but if it's running ok it might be best to leave it.
1986 Mk1 Golf GTI Cabriolet
Posted
Settled In
Ah right, I've seen them on ebay but ones I've seen asking price is usually around £100 each, which I can't afford without knowing that's the issue. I did strip my WUR and clean it out which has definitely helped, hence I want timing etc looking at first, but car doesn't seem to fast idle from cold which makes me think AAV still, I know it works as I've had it off and tested it. Plus now I seem to have a weak spark on cylinder 1 too
Yeah, I know what you mean, don't want to adjust it then the car not work at all, can always adjust it back I suppose. mines daily at the moment too so has to work, ish.
I appreciate the kind offer, but I'm on the Isle of Wight!
Posted
Local Hero
It's carb cars that normally rev higher when cold.
1988 Mk1 Golf GTi Cabriolet 1.8cc DX, K-jet. Daily drive. 317,000 miles and counting
1978 Mk1 Scirocco GLS 1.6cc FR, Webber carb. Weekend toy.
1978 Mk1 Scirocco GLS 1.6cc FR, Webber carb. Weekend toy.
Posted
Old Timer
I don't know how you did it but if you got 6 bar at the filter I would guess the problem is with the pressure regulator in the metering head. I know that adding shims increases the pressure but other than that I don't know much about it, perhaps you've got fuel leaking past the valve.
Posted
Newbie
It could be the pressure regulator in the metering head. Apparently though a 1mm shim adds 0.5 bar. When I checked the pressure regulator there doesn't seem to be enough space for all the shims I would need plus the spring. Maybe the spring has gone weak for some reason but I haven't been able to find a replacement.
I will buy the reseal kit for it though just to rule it out.
Something I did forget to mention, any pressure I do manage to create, if I turn the engine off that pressure will last for hours.
1986 Mk1 Golf GTI Cabriolet
Posted
Local Hero
86sam said
Something I did forget to mention, any pressure I do manage to create, if I turn the engine off that pressure will last for hours.
That residual pressure is a good thing.
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Posted
Newbie
Briano1234 said
86sam said
Something I did forget to mention, any pressure I do manage to create, if I turn the engine off that pressure will last for hours.
That residual pressure is a good thing.
I'm thinking this tells me the one way valve in the pump is working and the pressure regulator in the metering head otherwise it would just drain back into the tank.
1986 Mk1 Golf GTI Cabriolet
Posted
Old Timer
I would put new o rings in the regulator first and see if that restores the system pressure.
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