MK1 starting and running problems 😊

I have a problem with my MK1 GTI starting and running it starts first time every time it only runs for 2_ 3 seconds then cuts out I can hear the electric fuel pump on full ignition but as soon as it starts the pump can not be heard any help please let

Year and fuel type needed to be known, as in 85 GTI 93GTI.... as in CIS, Digifant, or Carbed.

Surely a GTI won't be carbed?

Red-or-Dead said

Surely a GTI won't be carbed?

Well on this side of the pond, the 1990's were Digifant 1 in California, but Digifant 2 in the rest of the US.
Digi1 has a coil pak, where the Digi2 doesn't and has a normal coil…. Biggest issues with Digi1 here are the Coil paks, that have cracks in the sealing at the bottom that allows moisture migration and failure of the coil pak..

From previous posts here there were carbed versions in 1990 across the pond.

From a PM, please when asked for information post to the thread as a post not a pm.

"1990 1800 GTi fuel injection model was stood for about 6 weeks fresh fuel added as well ."

Still I assume that he has Digifant2 but would like to see pictures of the engine… 1. to validate fuel type, and 2. then we can proceed to assist instead of wondering, and giving invalid tips.

When you insert the KEY in the ignition and turn the switch to run (NOT START) you should hear the fuel pumps Prime the system for 4 seconds, WAIT for the 4 Seconds prior to trying to Start.

This is normal behaviours of the system and starting Injected cars…Most folks don't….

If you try to start the car immediately, then you don't give the engine the chance to Build fuel pressures, and the duel system may fail to keep the pressures necessary for engine to run, specially if you have issues with the Fuel Pressure Regulator. You need to wait for the full 4 seconds.

After start you shouldn't hear the fuel pumps run, and if you hear a Whine from the right rear wheel arch then you have a fuel delivery issue usually with the in-tank pump.

The fact that you don't hear the pumps run after the engine stalls may or may not be an issue, why? because if the fuel pressure is correct, then the pumps stop pumping because they get the signal to fire and run from the coil.  Since the engine isn't running, then you don't have a signal from the Electrical controller to continue.

I would tell you that a few of the major iffy's I have seen on these critters, are the following.

The Blue CTS sensor goes iffy, I have personally seen them cause No starts when warm, No starts when cold and iffy running…"Lumpy" as you call it.

Fuel pressures check with the residual pressure tests, as that tells us the state of your fuel system.

Grounds.."Earths" they are everything to these guys.  a 1990 with still oem cables for grounds are waiting to present iffy electrical issues.  The normal grounds on these critters is an unshielded cable that is exposed to road salts in winter, battery outgassing causing corrosion and when that occurs then the path from the positive to the ground becomes resistive, and can change the values that sensors present to the ECU…Flakiness….

I have seen what looks to be good wires that are actually bad.  So I replace them . A 1990 has 30 year old OEM grounds???? Then replace them battery to frame, and frame to engine.

OEM rubber hoses leak, and cause false air reading, as it allows unmetered air to mix and this panics the hades out of the Digi controller (Vacuum Leaks) take  the idle bypass screw o-ring. bad o2 sensors, the list goes on and on and on…

As we don't know what has been done other than adding new gas.  So until we have other information we are just wondering in the dark and will stub our toes.

But I do know that replacing Grounds, and Cleaning the rest specially the one from the right rear Valve Cover Stud or o2 plug holder plate to the Coil Bracket can cause a wide variety of issues and is usually the first thing I suggest they do, you can use a set of battery Jumper cables to Temp Fix, by attaching the Battery negative cable from the Battery negative post to a good Frame point ie strut tower nut.  The take the red or Positive lead and connect that to the Battery negative post as well and attach it to the Engine Lifting eye to ground it as well.  Since the 1990 perversion to Plastic water flanges, the sensors now have to have a viable ground and those wires do go bad…if you have a flakey ground…and CTS signal strength can be lost.

Insert the Key turn to run for 4 seconds to hear it Prime, then start the car and see how it runs….

 

If it's firing up but only for a couple of seconds, it sounds like it's running on the cold start injector only.

It could just be that your mixture is not set correctly. Is this a new problem or has the car had some major work? If you have a long reach Allen key, try turning the mixture screw half a turn clockwise and see if it improves. Just make sure you count how much you move it so you can get it back to the starting point.

1990 IS CIS over there?  a good picture of the engine would solve a lot of questions.

If K Jet, carry out fuel pressure test as per the brown Haynes manual to establish if it's an issue with WUR or fuel distributor.

Also do a simple check to make sure fuel distributor plunger and air sense plate me are moving freely.

Also a thing to check is the auxillary air valve, when cold, it should pass air through which helps the air sense plate lift higher so you get a leaner mixture. The bimetallic plate heats up and closes the air valve and the idles should drop. Also carry out test for the Thermo Time Switch which triggers the 5th fuel injector during cold start for a few seconds.

This video is really good to watch
Bosch K-Jetronic (CIS) explained - YouTube

Good luck

Try a new fuel pump relay.