90 burban not running

I keep having a problem with my baby...the 90 burbazine.

While cranking, the fuel injectors intermittently spit out fuel. I have replaced the fuel pressure regulator diaphragm, carefully cleaned each injectors' filter, the vehicle's fuel filter, the fuel pump strainer, and the pump is roughly one year old.

Occasionally, the vehicle will start, run for about 30 seconds, then quit. It runs well, but then quits. When I try to re-crank, it will crank for about 10-15 seconds, then fire for just a few seconds. I will not be able to start again until a day or so later.

Another poster on another board suggested that it may be the ignition coil, or distributor pickup coil, as the computer may be getting a signal that there is insufficient spark, and not telling the injectors to open. I have an absolute behind-full of throwing parts at this rustbucket (plan on a body swap in spring 2005), but absolutely love my burban. Right now, the price of gas does not bother me, as I am getting real good mileage while it's NOT RUNNING!

I can hear the fuel pump initialize when I turn the key on, and have looked at fuel pressure with the line off, but admit that I have not tested pressure. I strongly believe that this problem is electrical, but may be very wrong.

Any advice is welcome.

Thanks.
Andy

I am having the same problem and it is a nightmare. I have replaced the Plug/Wires/Cap/Rotor/PVC. I am going to replace the fuel fillter next. I am very new to auto repair. I have found most of the parts based on browsing these forums looking for help. I checked for spark and will next check the fuel pressure as described. The motor has 99,000 on it and ran just fine until one day just started to hesitate and stall when coming to a stop or to turn a corner.
Hard to diagnose when it won't start and idle.

Have you checked to see if you have spark when it isn't working or if the spark is intermittenent? The ignition control module will shut down the injectors if it is not firing correctly.

No I have not. Cap & Rotor, and ICM are all fine; but have not tested spark. Never thought of no spark - thanks. Maybe coil?

If the ICM isn't new it may be bad. Even if tested at the parts store it may show up as good. The symptom you described (wont start again for a couple of days) usually means the ICM is overheating and shutting you down including the injectors. Look at the bottom of the module for an epoxy looking glue around the edges of the metal plate. That is a sure tell sign of overheating. (make sure the grease supplied with the module is coated on the bottom of the module this helps disipate the heat)

Check the coil thouroughly for cracks especially around where your wire plugs into it. The spark should be bright and crisp a week spark will not let it run correctly or even fire. The coil (plug) wire itself can also cause the problem if it is broken internally or shorting out.

Cranking it at night when there isn't any light will make a shorted (plug) wire or cracked coil spark show up real nice.

Been a while since I gave a thorough reply: I have replaced the coil, as it showed what I thought was a crack in the top of the unit. ICM looked fine. I have not actually checked the spark, although if this damned snow stops, I will tonight (getting tired of sharing the minivan with the wife). I have taken the pump oout of the tank, replaced the sock underneath, and checked fuel delivery all the way up to the throttle body - works fine, although have not checked actual pressure - delivers tons of fuel. When I used the fuel injector pigtail tester (light that plugs into fuel injector pigtail), it begins to light after about 2 seconds of cranking, then starts spitting fuel out of the fully connected injector, fires weakly (as it's only getting fuel in 1 bank, right?). I re-connect the injector pigtail then it goes back to firing whenever. I get absolutely no trouble codes in the ALDL, just a continuous flashing 12. Short of the weak spark that I haven't yet checked, am I missing anything? Could it be a bad ECM? Please help, and thanks already for your input.

Andy

I doubt it is the ECM (actually ECC). It is rare for that to go out. But is possible. Check for the spark. if it is not present replace the ICM. A simple test on the pump to tell if you are getting pressure is to attach the pos. lead of your volt tester to the fuse and of coarse neg to ground when the key is turned on you should get 12 volts, after a minute or so it should lose the voltage this would indicate you reached pressure.
If it keeps kicking on and off then it is not maintaining pressure.

Would the absence, or weakness of spark be cause for the injectors to not open?

You've been extremely helpful. Thanks again, so much.

Andy

Yes it will.

I will probably try again tomorrow. Hopefully this snow will stop soon. Thanks again, very much.

Andy

PEOPLE HOW MANY TIMES DO I HAVE TO SAY THIS NEVER ASSUME A PART IS GOOD OR BAD UNTILL YOU TEST IT. Stop waisting your money and tell me what is the fuel pressure reading with key on and while cranking. You guys want to dump tons of cash on a problem in hopes that you stumble on the answer. GM's number 1 drivabilty problem is fuel pressure with out knowing what your is then your just waisting your time and money and these days who can aford that. Just because you hear the pump that dont mean squat you must get a reading.
Sorry about the speach but it just seems like a lot of want to be Techs just love to throw parts at a problem and sooner or later they will get the right 1 after a ton of cash is spent.

I would just as not spend any money till I know what the sure problem is. Narrowing down the problem with a few easy tests gets you closer to the "root cause" and takes out the guess work.

Fireplug-
Thanks for the response. I did not check with a pressure gauge, but shall, forthwith. I had not checked spark, and figured that was a cheap test, and would like to eliminate that as a problem. My next question to you: When the fuel pump initializes, does it stop when it reaches required pressure, or does it just act as a preset "prime" amount (like a well pump)? Next, when I do go get the fuel pressure tester from Autozone, do I put it anywhere inline - for example, can I take an end off the input side of the filter and then place the pressure tester in the line coming from the tank? I only ask because I have never done it before.

Again, I thank everyone for their spirited input. Seriously, it is all good. Thanks, folks.

Andy

There is a test point on the fuel line up on the intake manifold area. Just follow the fuel line from the injectors back and you will find it.It looks like an A/C Fitting. Its a schreader type valve just screw it all the way on and then turn the key and see what the reading is. Now some good test gauges have a bleeder valve on it to dump the air in the test gauge line. Have a rag handy and just crack open that bleed valve. The turn key off for about 1 min then turn the key to the on position and get a true reading. The pump will only run for about 1.5 to 3 sec total time if the engine is not cranking over. Turn key off and see if it holds pressure or bleeds its self off. You want to see it hold the pressure. Then have some one crank it over while you watch the gauge and get the cranking pressure.
Please post what you find.

Fireplug,

I have a 90 Burb also and had the fuel filter clog up. It got to where I could do no more than put a slight pressure on the pedal before it would start choking from lack of fuel. It took me quite a few miles to figure it out so now I am wondering if I have done any damage to the pump (it seems to have a SLIGHT flat spot at half throttle if I do not "ease into" the pedal.

What should the pressure reading on this 1990 350 be (thinking of going to Autozone myself and renting a gauge)? I found a post listing the pressure at about 60-65 psi but it was in reference to a 2000 model.

Thanks for elaborating on the test procedure - it may very well help a couple of us out.