Need Help With 99 Turbo Fuel System

[TurboBudapest]

Hello Everyone,

I would need help with my 1978 99 Turbo, and thought I would turn here for ideas.

My car has been completely rebuilt and all parts which could be replaced have been. The one part of this car which has been its achiles heel is its fuel system. The car used to have the steel tank in it, which would gum up the fuel system terribly with bits of rust and other debris. Since then we have changed the fuel tank to the one or two model year only 900 plastic type, but the fuel system has never been the same. It has received several replacement fuel pressure regulators and warm-up regulators, but I am at the end of my patience....it still does not run as it should - and in fact, the engine jerks at around 3500 RPMS right when the fun starts with a 99 Turbo.

Ideally I would like to install a new fuel pressure regulator, a new warm-up regulator and new injector heads. The problem is that these parts are very hard to come by.

On the warm-up regulator, my car has the vacuum operated version which is difficult to get new. I have found this website which rebuilds them, but it is expensive (especially with shipping), I have to send in the old unit for refurbishment (so have to pay postage both ways), and the website is somewhat confusing and not very confidence inspiring: http://specialtauto.com/warm-up-regulators.html

On the fuel pressure regulator, the situation is pretty much the same. I found various websites offering rebuilds, but the sites are for the most part confusing and not very helpul.

Does anyone have any experience with these things who can offe me some help? I attach a picture of my steed for those of you who are interested (I love this beast).

Thanks so much!

Ed

[DrewP]

Someone posted a copy of the K-Jetronic manual I think that has trouble shooting steps in it, but I can't find it after a quick search, but I did find this: http://www.porsche924-944.nl/924/Troubleshooting.html

Did you pull the injectors out and see how they flow? It could easily be injectors if you haven't checked them. If you pull the injectors out and stick them into little cups to catch the fuel, you can jump the fuel pump to run, remove the air intake boot to the fuel distributor sensor plate, and lift up on the plate with a magnet or something to get some grip.

The higher you lift the plate, the more fuel should spray out.

All 4 injectors should have smooth, uniform, triangular spray patterns. If some (or all) have little areas that are squirting jets of fuel out rather than making a nice mist that may be your problem.

[Crazyswede]

What are you running for spark plugs? Have you checked valve clearances recently? Good cap rotor and wires?

[TurboBudapest]

Thanks to the both of you for your replies to the above.

I ended up going through the whole fuel system. Turns out that the fue injector head was full of rusty metal bits, the injectors were shot and the spark plugs were all very dirty/coroded.... Also the warm-up regulator was not working. The main culprit was the rusty tank which was on the car till about two years ago. Even though it ran 3000 miles or so on the 900 plastic tank (the early one which is a direct replacement and was made only for two years), there still was enough junk in the lines which was screwing with the fuel delivery. Since certain of the cylinders were running richer than others, the combustions were not as clean as they should have been which caused the spark plugs to get dirty/coroded (I am not a mechanic, but this is my understanding).

I purchased brand new injectors off of ebay and had them installed, along with a good used injector head (good maybe too strong a word - perhaps not too bad would be more accurate), a good used warm-up regulator and new spark plugs and the differrence it made is night and day. The car runs soooooo much better I cannot even explain. It is set a little too lean at the moment, but we will play around with the settings.

At some point, I will have to send one of my non-working injector heads for reconditioning to a specialist (very expensive, but probably would be worth it).

Am loving driving the 99 Turbo again. I remain convinced that this is one of the most characterful cars on the road today!

Thanks again!

Ed

[DrewP]

That's awesome!