Dilemma, fuel injector or not maybe who knows!

Heyyy all you willing mk 1 owners, have a go at figuring this one out please!

ok , had a mis fire on idle which gradualy went under revvs, checked plugs and one was heavilly sooted up, the spark was strong and good.

so got a new injector, put it in but still did not sort the problem, so took the intermediate line off and that was clear, changed the fuel filter (engine bay one) and that was full of crap. but still running lumpy on idle, so stupidly…

took off all the little cap screws (torx ones) out of the metering head and removed the tapered grub screw with the little rubber seal out of the troblesome line connection.

started her up and revved, fuel came out then stopped, put grub screw back in but guess this has an exact setting and put torx screw back, started her up and it was ideling perfectly…

and fires perfectly on slow revvs…

but under heavy load ( hard acceleration)  it seems to loose power , its hard to explain , but intead of revving it sounds like im hitting the revv limiter, fast rumble sound of a missfire of some sort

ok so this is where im at, what have i done wrong?  

because whatever i have done has helped it idle better but now missfires with heavy revs..

any help will be greatly appreciated

PaulC-J said

Heyyy all you willing mk 1 owners, have a go at figuring this one out please!

ok , had a mis fire on idle which gradualy went under revvs, checked plugs and one was heavilly sooted up, the spark was strong and good.

so got a new injector, put it in but still did not sort the problem, so took the intermediate line off and that was clear, changed the fuel filter (engine bay one) and that was full of crap. but still running lumpy on idle, so stupidly…

took off all the little cap screws (torx ones) out of the metering head and removed the tapered grub screw with the little rubber seal out of the troblesome line connection.

started her up and revved, fuel came out then stopped, put grub screw back in but guess this has an exact setting and put torx screw back, started her up and it was ideling perfectly…

and fires perfectly on slow revvs…

but under heavy load ( hard acceleration)  it seems to loose power , its hard to explain , but intead of revving it sounds like im hitting the revv limiter, fast rumble sound of a missfire of some sort

ok so this is where im at, what have i done wrong?  

because whatever i have done has helped it idle better but now missfires with heavy revs..

any help will be greatly appreciated

Have you measured the mixture with any type of tool? Or the fuel pressure?

Not the fuel pressure or mixture because it has always run perfectly on these settings since i bought the car, do you think changing the fuel filter has allowed a better flow? alterting the pressure and now overueling maybe..?

Basically, until you actually measure the mixture, you're guessing! You've been swapping components and taken apart/put back together the metering head, or components within, which all affect the mixture. Fuel filter isn't one of these but if you had a blockage which was intermittent but is now free, you'd instantly see this with a fuel pressure check.

Also make sure the ignition system is fault-free.

thanks…

so your saying that if the fuel filter was blocked and now its not the charitristics of the fuel delivery have been changed… and i know i won't know untill i get a co2 reading but maybe overfueling under load?

also know its asking alot but how is a fuel pressure test undertaken?

PaulC-J said

thanks…

so your saying that if the fuel filter was blocked and now its not the charitristics of the fuel delivery have been changed… and i know i won't know untill i get a co2 reading but maybe overfueling under load?

also know its asking alot but how is a fuel pressure test undertaken?

No, I'm not!

Ok put simply, ANY problem can be solved by:

1. Having a reasonable understanding of it
2. Measuring things
3. If/when these are out of specification, tuning or adjusting somerthing to bring it in spec


For the fuel injection, I'm suggesting step 1 is to take a step back and ask yourself if it really is the fuel injection, or the ignition. After all, a "poor running" engine can run poorly for any/all of these reasons:

1. Ignition
2. Timing
3. Compression
4. Fuel mixture

and only one of these is controlled by the K-Jetronic fuel injection components……