1989 16V no start

Fuel pump relay? Bypass the relay and power the correct or large(?) terminals to power the fuel pump to see if it starts.

I tried that first. But that's when the knock box fried. There is power to both pumps and I can hear the main pump run. I can't be sure that tapping on the relay was just a fluke. I would like to test a fuel injector to see the spray pattern or even if it's spraying fuel but I'm not sure how to do it correctly. I pulled the injector out and grounded the body of it and turned the motor over (grounded coil wire) but it didn't spray. Did I miss something?

If just jumping the proper terminals at the fuel pump relay caused the knock box to fry...........then there are other problems. :-( Unplug both fuel pumps and check the drain across those relay terminals. You could test it with a inline fuse kit to see if the fuse blows. Any rodent problems?

The cold start valve/>> Fuel pump relay?

I did replace coolant temp. sensor and therm time switch. Also repaired some marginal wiring to temp. sensor. I seem to have a lot of parts laying around from my other 16V. Now if I disconnect both pumps what am I measuring across the fuel pump relay? I'm thinking a correct measurement would be battery voltage. I did get a good spray pattern from the cold start valve with no drip at shut off.

Funny you mention rodent problems. I have a 1982 GMC 1/2 ton with a

350 in really good shape. It doesn't get driven much so mostly it just sits. I popped the hood one day in the fall just to check stuff out and when I opened the hood the ENTIRE engine compartment was buried in pine cones. They were everywhere. In every little crevice. Between my header tubes, in the fender wells, under the carbs...it was amazing. Then I looked in the glove box for a battery receipt and every piece of paper was gone. I found it all later...shredded up to make a nest in the hood latch opening. He doesn't live there anymore. But this Jetta doesn't have any rodent issues that I've found exept maybe gremlins-but they all do at some point.

I believe if you are measuring the amperage with the fuel pumps disconnected it should be close to '0'. I think the only things that relay might power are the fuel pumps. Not sure if it also powers the either the frequency valve or the electronic fuel pressure regulator or ???. Not sure how the knock box died! hmmmm I would need to see the wiring diagrams.

Maybe you can get some info from this url on your knock box.

I looked at the wiring schematic for the 88 ( no 89 listed :-( bummer )But there is a 10amp fuse between the coil and the two switches forthrottle position, and on the 88 diagram there is a feed to injection controlfrom the knock box. Rodents : I use mothballs in 6 x 6 inch pouches made out of window screening ( kinda like a envelope stapled on the sides with a fold flapon top so you can replace the mothballs after they get old) in placeswhere the rodents like to build there houses. Two of these under the hoodof my 83 powerwagon ( a beater used only for snow plowing) keeps rodentsaway. I also put these mothball pouches in my JD lawn tractor and an ATV. I remove the pouches when I use the vehicles so I don't have to smell themand replace them after use. A pain in the butt , but since I've been doing itI have not had problems with rodents - I wonder what works for gremlins?

I wish that did work for gremlins! lol Also you could try some bars of Irish Spring soap. I hear it works as well as mothballs but has a better smell. ;-)

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I'll have to go check the amperage and look for some fuses. I have the wiring diagrams but for some reason they seam incomplete or at least they don't show the full circuit from start to finish. As an aside... I tried the soap trick...but the little bastards ate it. That might of been Zest soap though.

gremlins?- Hide quoted text -

OK...so it started. Why, I'm not sure. All I did was clean the plugs and replace the knock box. If I turn the motor off it only wants to start on the second or third try. I'm thinking maybe fuel pressure related but it's cold and snowing right now so more diagnostics will need to wait. Thanks everyone for your help.

Dirty mouth little rodents! lol

glad it started but I still don't trust it!

I don't trust it either, so now every time I take my dog out, I try to start the car. So far it's started every time-first crank. Thinking maybe a loose wire to the relay at the fuse box or some other hidden demon.

OK

Well...dammit!! 4 days went by and now it won't start again??? I didn't actually look at it, just tried to start it and it just turns over. Accumulator, regulator...help!

needs; spark fuel compression

what is miss>> >>

My guess would be an electrical open for the electornic control of the injectors. Maybe power supply related at the fuse/relay box. Any signs of water drips under the dash? ( blocked drains in the cowl drain) Intermittant faults are a hassle to locate so keep your troubleshooting/inspections to one area before trying to get it to start. And one thing I'd try which is 'accumulator in mind related ' turn the key from off to run ( no start ) five or six times then try to start. I'd try this test first before even popping the hood release.

Allright, first things first...it has air, fuel and spark. Comp. is good-190 across 3 and 180 in the last one. After I turn it over with the resulting no start the plugs are wet with fuel. That leads me to ignition. It has a good blue spark at all

4 wires. I have tried running the pump with the key 5 or 6 times before cranking and no luck. Here's the thing that's got me beat. When I do get it started it runs like a top. Good power, smooth idle, no vac leaks and good throttle response. I haven't been able to find anything obvious like water on the box, carbon tracks in the cap, bad grounds or anything else. The previous owner assured me it never behaved like this before. I'm thinking it may just be a matter of time before the car knows that I will love it as much as my other 89 16V. Thanks for all the tips. Tomorrow is the weekend so I will start over with the simple stuff first. I'll keep you posted. If anyone can think of something I missed, let me know. It's not a parts car YET.

OK then it is either the spark plugs not firing under compression or the spark is not hot enough. First I would change the spark plugs. Which ones are you running? Bosch triple tip or silver tip?

Then possibly the ign. coil if you still get spark to the new plugs and they come out wet.

I will assume that you have GAS in the fuel tank! 8^)

Oh and how did you check the spark? From the ign. coil or from the distributor? If from the coil maybe the distributor rotor, cap or wires are bad.