Author Topic: 98 Mk3 fuel starved  (Read 3368 times)

Offline gaynord

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98 Mk3 fuel starved
« on: 01 December 2017, 22:12 »
Hello I’m posting this again as although I’ve had one very helpful response I think that I probably posted it in the wrong place as I haven’t used a forum before.  Looking at other threads there seems to be a lot of really useful info out there and I hope I’ll be able to get it fixed.   I'm currently in Oz trying to repair my wifes 1998 VW Golf Mk3 1.8  petrol car which just won't start.  It's done around 76K and was running fine until it just cut out one day it then re- started straight away but the next day only went about 100 yards before  stopping and I haven't been able to restart it since.   If I spray easy start down the air intake hose it starts straight away and runs until that has gone but that's all.   It has good sparks at all the plugs and I'm pretty sure it's all to do with the jetronic/monotronic unit but as I don't really understand how it works I'm really struggling.  I've taken it off and cleaned it with throttle body cleaner and cleaned all it's electrical connections with contact cleaner but when I re-assemble it it's just the same.   I removed the two fuel hoses from it and put them into a plastic bottle and when I turn on the ignition the fuel pump pumps fuel out. I can't see any fuel coming out of the jet above the throttle butterfly and I think I should be able to.   I did think that I would try and find another one in a breakers yard and fit that to see if it worked but as they're not a very popular car here I haven't been able to find one.   Also I suppose that it may be the electrical system not sending the power to the unit that's the fault so I could waste time and money fitting another one only to find I still have the same issue.  is there anyone who knows if I can test this unit somehow? Or is there some way of isolating or bypassing the electrics to eliminate them?  Any helpful ideas would be most welcome.  What makes it worse is that it's automatic so I can't tow it down the road to see if will go and I have to keep charging the battery.

Thank you for looking

Offline gasketface

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Re: 98 Mk3 fuel starved
« Reply #1 on: 03 December 2017, 10:49 »
Are you sure its got a spark as it sounds like coil pack or crank sensor to me.Maybe an immobiliser fault (relay)

Offline itavaltalainen

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Re: 98 Mk3 fuel starved
« Reply #2 on: 03 December 2017, 19:32 »
The 1.8 has a few weak spots. Cleaning the TB really is the one thing that isn't necessary on these though (get's constantly sprayed with fuel as is).

- ignition coils (as on all mk3s)
- flange between mono injector and manifold (likes to rip and let unmonitored air in)
- idle adjuster gear (plastic gears brake)
- wiring to injection (pull the rubber grommet back from the two plugs that go onto the injection unit)
- hall sender, though this is quite rare compared to other issues

I don't think this is immo related, but it would help to get fault codes anyway.


2019 Seat Leon ST FR DSG 135kW - eclipse orange - 23k miles

Offline gaynord

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Re: 98 Mk3 fuel starved
« Reply #3 on: 04 December 2017, 07:56 »
Are you sure its got a spark as it sounds like coil pack or crank sensor to me.Maybe an immobiliser fault (relay)
Yes it has a good spark at all the plugs, I’ve had them all out and lined them up on the rocker cover and watched them in the garage with the lights out as I crank it over and as I say it runs as soon as you squirt easy start down the air intake.  If I hold my finger on the aerosol nozzle it will keep running until I stop squirting it