(These are post repair comments. The following series of posts can be summed up as follows: we fixed the problem by crimping the spider electrical connector and installing new spark plug wires. These solved the intermitent fail-to-start and rough running problems. The other new parts may have helped. What an adventure getting to that point. Thanks to all esp Swart)

I looked at several tech posts and did some searches but didn't find an answer to this. Is there a way to bench test the pressure reg and spider?

I have checked fuel pressure - good at 60 psi with no bleed down. Plugged a GM PFI noid light into the central port injector connection and got pulses. Spark is ok. Scanner says there is a fuel supply prob - I did not do the scan and do not know what the codes are. Tailpipe is not sooty; it's quite clean. Have yet to pull any spark plugs.

Pulled the air flow regulator (it was stuck so I worked it a bit and lubed it now it springs back like is should). There is no evidence of a leak in the pressure reg - with the ig on there is no sign of a leak; the driver's side of the plenum looks a little coppery but so does the drivers side. No strong gas smell or pooling. Poured about a 1/4 cup of gas inside the plenum, replaced the air flow reg and cranked it over - started and would rev nicely then eventually die and fail to restart.

I can get a spider for about $315 remanufactured, FPR for about $30 and hose (nut?) kit for about 60. Would prefer not to replace the spider unless we have to. I guess I could replace the FPR, put it all back together then see if that fixes the prob.

Long story is it belongs to an umemployed 23 year old divorced mother. We are trying to get it fixed for her under really bad circumstances. Her own mom is in the hospital seriously injured from a pipe bomb explosion and her dad has been arrested for planting the bomb!

 

If the pressure holds steady, then you do not have any leaks and the FPR is likely good.

Have you tried providing power and ground directly to the injector with the fuel system pressurized to observe the spray pattern out of each of the poppet nozzles?

 

Thanks Swart. I appreciate all your posts and help and the posts of others on this subject. They have been a great help. In your comment above I guess you are suggesting I take the plenum cover off then observe the spray patterns as a way of determining if the spider is good?

We are thinking that if the spider is the problem, that together with the possibility that the cat is bad and the rust damage to the body, that we should probably just sell it for parts and buy the daughter another car.

 

Observing the spray pattern from each of the injectors is really the only way to tell if the spider is good/bad.

A bad spider can clog up a cat quick.

I'm not sure I would part out the truck over these things though. A universal cat ($60) and a spider ($300 or so) and you'll be back in business. You'd be hard pressed to buy another car for that much even offsetting the cost by parting out the truck.

 

I decided to follow your suggestion since it wouldn't cost anything but time to do the test. Took off the plenum cover and noticed something funny - someone had twisted each pair of the spider wires together and did a little soldering but did not insulate the connections. Had my son crank her over and two of the injectors I checked squirted and it wanted to start. So I insulated the two bare wires and reassembled - seems to run fine!

Now I get to figure out if there are other issues.

Thanks for all your help.

 

It looks like I may have found the gremlin but I still have some questions. After I insulated the wires to the spider it started great and ran pretty good. But after driving a while it died. Then it would restart and drive short distances before dying again. Also did not have temp at the instrument cluster.

Plugged in an EZ 6000 scanner I borrowed. Scanner said the TPS was low so I replaced the TPS. Still read low so I replaced the TPS a 2nd time. Still read low. But the starting/running problem only got worse - sometimes it started, other times it would not start. Tried the wiggle test. Also replaced dist cap, rotor, wires and plugs.

I was not confident of the scanner so I did the flashing light/paper clip trick to get any codes. Got three sets of two quick flashes. Anyone know what tha code means (searched on here but could not find)?

Next I pulled the air flow regulator then removed and reconnected the spider electrical plug. Since then it has started every time and the temp gauge works!

I would stil like to know what the scanner outputs mean. Anyone have a link to a list of specs or values for example for the MAF sensor, the O2 sensor, etc?

 

The best test for the TPS sensor is to just use a multimeter. One wire should have +5V, then there's the ground, and finally the return to the ECM. Closed throttle, the return should read around 0.5V. At wide open throttle, it should read around 4.5V. It doesn't need to be precisely on those values.

As far as sensor readings go, you don't have a MAF and the O2 sensor should bounce between ~200mV & ~800mV as it transitions from rich to lean.

The MAP sensor should have a voltage output proportional to the manifold vacuum in the engine ranging from 0V (high vacuum) and 5V (low vacuum). The output voltage should be 3.0-4.6V at 4k-5k above sea level with the engine off. Pull a vacuum on the MAP sensor to around 10 in-hg and the voltage should drop 1.0-2.5V from the atmospheric condition.

BTW, I combined your threads back into one. It is a bit cleaner this way since you never really fixed the problem in the first thread. If someone reads through this with the same symptoms later on, it is easier to have it all in the same thread.

 

Thanks again.

Based on your specs the old TPS is still good . We bench tested it and got what I thought were good readings but the scanner said it had low voltage. The MAF voltages are in the range you suggest. The O2 sensor varies between about 100 mV and 850 mV through the range of throttle from idle to about 3K i.e. whether I hold it at steady idle, 1500 or 3000 rpm the readings flick between about 100 and about 850. The mV readings are not near constant at constant throttle. Is that normal?

Although the motor seems to be running very well now I think I also feel/hear a slight mis at idle. I don't seem to notice it at higher rpm.

We are at 650' elevation. We haven't had a smog test done yet. It is not a CA vehicle.

 

The ECM is continuously changing the IPW (injector pulse width) varying the air fuel ratio which is what the O2 sensor detects through the presence of free oxygen in the exhaust. As such, it is completely normal to see the values bouncing around.

Below 1000' above sea level, the MAP (manifold absolute pressure - not MAF) output voltage should be between 3.8 & 5.5 according to my reference. Not sure how it outputs more voltage than it receives, but...

As far as your dying problem, if you haven't done so already, remove the ICM and take it to an autoparts store that has a compatible tester. Have it tested at least 10 times in rapid succession.

 

Here I am back again after letting the small blazer sit for a month. Starts pretty good and revs fine but under load it misses badly; if I pump it I can get it to rev quite high but it misses when trying to accelerate.

To recap - spider test seemed to show it was good, fpr is good, air flow regulator is not stuck, new ICM, new TPS, new plugs, wires, dist cap, rotor, used noid light to check injector pulses, EZ 6000 scanner not throwing any codes, fuel pressure is good.

Any other ideas - spider, ignition coil, fuel filter?