Mk1 jetronic injection wont restart.

Hi All, I was once an auto elec in the past so I still know a little!  just!

I have a Mk1 golf cabby, its mechanical injection.  Engine runs great never fails when running.  But once shut down is often impossible to re start. Cranks like a demon, I have spark and timing seems correct.  Compression all ok too.

I dont seem to have fuel pressure.

I can leave the car for a day and then bang starts again no problem, park it and again wont start. repeat.

How should a trouble shoot this?

Cheers Paul.



 

sounds like the fuel accumulator is broken. you can check it buy removing the small screw in the back if fuel comes out it is faulty

looks like this

Common issue is the starter motor breaking down.
My old cabby used to do it once the car was hot and I'd turn engine off it wouldn't start.
I had thoughts of the immobiliser and all sorts of stuff.
Plus the wiring gets old and the resistance gets higher.
On mine once I replaced the starter I had no further trouble.
There is a relay fix.
Just google hot start relay in the google search box on here.
Iirc there's a diagram on one of the posts.


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chortle said

Common issue is the starter motor breaking down.
My old cabby used to do it once the car was hot and I'd turn engine off it wouldn't start.
I had thoughts of the immobiliser and all sorts of stuff.
Plus the wiring gets old and the resistance gets higher.
On mine once I replaced the starter I had no further trouble.
There is a relay fix.
Just google hot start relay in the google search box on here.
Iirc there's a diagram on one of the posts.


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No no cranking is not an issue, cranks like a demon.  Has spark wont fire. Other times starts first hit.  seem fuel related.

sporttrucker said

looks like this

Thanks, could this explain the intermittent nature of the re starting? Also note, that to date once started never fails until next restart.  Has plenty of spark.

I recently powered the fuel pump near the RHS rear tire. Then  cracked the fuel fitting at the under hood fuel filter and fuel sprayed everywhere!!!!  With the pump powered like this it would still not fire.

sporttrucker said

sounds like the fuel accumulator is broken. you can check it buy removing the small screw in the back if fuel comes out it is faulty

Hi,

Is this item easily located?

Also Id be interested to know under what circumstances does the fuel pump kick in? Because  when I turn the key on there is no pump sound.  Im told that the fuel pump wont kick, in for safety reasons until the starter is cranking.

I can confirm that when cranking there in NO fuel pump action!

Hi Palmac

Are you sure the pump isn't running when the starter is cranking, they are quiet when they're in good condition.

I think you ought to work out first of all if it's problems starting when warm are from not enough fuel or too much, when it does start does it just run normally or does it cough and splutter, run perhaps on three cylinders and then sort itself out, if the latter then it's probably too much, if the former then not enough..

When it's playing up take the plugs out and see how they look, see if they're wet, if they are it could be the injectors are dribbling fuel. The thermo-time switch could be playing up aswell, try taking the wiring connector off the fifth injector.

A pressure gauge is almost essential when you get problems, if you intend keeping the car it's worth getting one, it's the only way you're going to check the holding pressure, system pressure and control pressure, makes you feel a bit professional too.


 

Hmmm there's two sorts of fuel pump relays and two fuel pumps. One in the tank and the underbody one.
One type of relay has an extra pin it's a five pin relay. It energisers sensing from the coil inturn energisers the intank lift pump and under body fuel pump on the turn of the key allowing priming of the system.  
What can happen also is the current through the relay causes them to overheat and fail. It maybe worth checking the condition of the pins for corrosion and overheating
I've heard of this issue actually causing the fusebox area to melt.
I had an issue that mine kept blowing the fuel pump fuse.
This was down to rust in the tank which blocked the in tank lift pump and the fuel filter was disgusting.
A clean out of the tank, a new lift pump, fuel pump relay I was good to go.
If it's not cranking over it's likely to be electrical.

 


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it is near the fuel pump under the car, the accumulator regulates the fuel pressure and flow and when switched off it holds the pressure in the lines, it has a spring and diaphragm inside so if it ruptures it wont hold fuel pressure up which will affect hot starting

No, the accumulator doesn't regulate the flow or pressure, it just holds a limited amount of pressure in the lines, I forget how much, which prevents the fuel from vaporising and helps starting so you are right, If it were faulty it could effect the hot starting.

kind of does, the fuel hits a baffle as it enters the accumulator and there is a sprung diaphragm inside it which the pump is working against, so will effect the pressure and flow, but would still do so even if it is ruptured, there is no valve in the accumulator just the non return valve in the pump

if the fuel pump(s) definitely not running while cranking, theres your problem.

for testing swap a 17, 18 or 100 relay into slot 2 this will make the fuel pump always come on with ignition. if the pump(s) comes on and it starts then either the relay is bad, fusebox or the rev counter wire that triggers the relay from the coil to fusebox is crusty, start at the coil end to make sure all is well there

if the fuel pump(s) dont run check fusebox, fuse and pump wiring. if pump runs but no fire look at the spark system, as above it needs a rev counter signal to trigger the relay. if thats missing this suggests you have hall sensor troubles, wirign fault or the spark module is failign when hot

Problem solved.  The issue was the ignition pulse triggered fuel pump relay was faulty. I decided to just power this circuit with ignition via a regular relay which means that the pump starts as soon as I turn the key on.  That will work for me.
Car is running well again

GSF do new fuel relays, having it on all the time with ignition isnt ideal as its not safe if you crash the car

rubjonny said

GSF do new fuel relays, having it on all the time with ignition isnt ideal as its not safe if you crash the car

X47……  

rubjonny said

GSF do new fuel relays, having it on all the time with ignition isnt ideal as its not safe if you crash the car

I'm of course fully aware of that! Even so I'll take my chances, till I can pinch one from the auto wreckers! I'm like that…..cheap!

palmac said

I'm of course fully aware of that! Even so I'll take my chances, till I can pinch one from the auto wreckers! I'm like that…..cheap!

Cheap is one thing, Cost-effective is another, and you are betting your life on it…. Or the life of the one in your passenger seat.  Solicitors being 1 half Darwin Pip above Trailer Trash, and Rats, will tend to get major bucks from a accident, if you are at fault and knowingly operate a Car in a unsafe manner.

My two Pence….

just sorted this same problem on mine
turned out to be the non return valve on the fuel  pump
it had seized open so all fuel pressure was lost and was impossible to start when warm
cheap place to start to investigate small part between the pump and bango fitting about £10
sorted mine