1995 Chevy Van TBI Injectors not firing

Tiny
STUDEBAKER14
  • MEMBER
  • 1995 CHEVROLET VAN
  • V8
  • 2WD
  • AUTOMATIC
  • 178,000 MILES
Greetings,

I really appreciate your website and making your knowledge and experience available to us shade-tree mechanics.

My problem child is my 1995 Chevy Beauville Van, 5.7 TBI, 4L60E Trans (I think), It’s really in great shape and I plan to repair the rusted lower body panel and make her new again. But she’s currently giving me fits.

I worked on it one evening, installing some fog lights. I ran my fused switch line to the a pin on the fuse block. Job was done, I shut her off, and went in for the night. She would not start the next morning.

The truck has it’s original fuel pump (which I admit still could be the problem if there’s not ENOUGH fuel pressure). However, when I jump the FP Relay, and crack the fittings at the base of the TB, II get a very healthy spray. If I pour raw fuel into the TB, she will light. I don’t have a fuel pressure gage to check, but I believe the pump to be OK.

I have replaced all the fuses and Circuit Breakers. On two occasions the van DID start, but ran very rough. I attribute this to the FP Relay fluttering as I had a test light connected to ground and the relay activation lead. It flashed wildly and pulsed to the engine ignition. Eventually the engine would die, not to start again. This is what leads me to believe that this is an electrical issue.

She turns over freely. No known mechanical issues. I have + power to the injectors but they are not activating that I can tell through my stethoscope (long screwdriver to my ear).

I have swapped the PCM with a known good unit. I have also replaced the FP Relay. If I jump the relay, the pump runs at the same pitch as it always has. Sound just like the one in my 1995 Caprice. Are there any fuseable links or hidden fuses I should be looking for? Everything seems tobe in order under the dash. This has not been all cobbled up like so many old vehicles. It’s all original and in very good shape.

So, assuming there is adequate fuel pressure from the pump, the PCM is good, all the fuses are good, the FP Relay is good, there is good gas in the tank, the battery is strong and connections are clean, what am I missing?

I am hopeful you can help me. My job is depending on this van.
Sincere thanks,

Chris Baker
Studebaker14@comcast. Net
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Saturday, January 10th, 2009 AT 6:01 PM

20 Replies

Tiny
RASMATAZ
  • MEMBER
Check the fuel pressure and get back

FUEL PUMP PERFORMANCE

5.7L (VIN K) 9-13 psi
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Saturday, January 10th, 2009 AT 6:27 PM
Tiny
STUDEBAKER14
  • MEMBER
Will check that tomorrow. However, I feel the pressure is there. Assuming it is, after all of this, what would prevent the FP relay from engaging? It appears (if I got the right wiring diagram) that I'm not getting power to the relay or possibly the PCM, thus preventing the pump from running and the injectors from activating.

BTW, There is good 12VDC + at the injectors. Rechecked all the plugs.

So, if everything else is checking out OK, I guess my question is what would cause the FP relay to flutter? Could the pump put such a drain (dragging) that it would cause the relay to disengage? I would have my doubts, but I'm not the expert.

Thanks guys!
Chris Baker
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Saturday, January 10th, 2009 AT 6:45 PM
Tiny
RASMATAZ
  • MEMBER
Its the computer that energizes the fuel pump relay and also drives the ground circuit for the injectors-recommend you check the wiring and also for shorted injector that's taking out the other


http://www.2carpros.com/forum/automotive_pictures/12900_fuel_pump_and_oil_pressure_sending_unit_1.jpg

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Saturday, January 10th, 2009 AT 7:04 PM
Tiny
STUDEBAKER14
  • MEMBER
OK. But I swapped computers with a known running van of the same year, make and model. My computer runs that van fine.

Pardon my ignorance, but what would then be between (or before) the Computer under the seat and the relay and injectors that could cause this?

I've never seen anything like this. Also, I have great spark from the dist to the plugs.

Thanks for the diagram. Where would that test port be located on my van?

Truly, many thanks for your help.
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Saturday, January 10th, 2009 AT 7:11 PM
Tiny
RASMATAZ
  • MEMBER
What type of fuel system do you have? TBI/MPFI/CPI Vortec? Not to familiar with vans-If its a vortec-you should be able to see the fuel test port when you follow back to the rear from the upper plenum
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Saturday, January 10th, 2009 AT 7:37 PM
Tiny
STUDEBAKER14
  • MEMBER
It's the last year of the previous generation of full-sized Chevy Van (boxy), So it is TBI--fuel is fed into base of TB and injected thru the 2 injection over the throttle butterfly.


http://www.2carpros.com/forum/automotive_pictures/277597_100_3140_1.jpg

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Saturday, January 10th, 2009 AT 7:49 PM
Tiny
RASMATAZ
  • MEMBER
Get helper to crank her over and look at the injectors are they spraying fuel in a cone looking shape-

The fuel lines is behind the TB follow the feed if there's no test port T the fuel filter
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Saturday, January 10th, 2009 AT 9:14 PM
Tiny
STUDEBAKER14
  • MEMBER
Already known. There is no fuel coming out. When I jump the FP relay, the FP runs and sound absoutely normal (I know, not a real indication of performance, but is't a start).

When FP is running, I can crack the fittings at the base of the TB and get a strong spray. What I've narrowed down is that the FP relay is not being activated when KOEO (key on-engine off) position. It should activate for approx 3 seconds as a prime to stat the engine. At this time the engine is supposed to start and the oil pressure sensor tells the PCM to continue pumping fuel. None of that is happening.

Thanks
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Saturday, January 10th, 2009 AT 9:35 PM
Tiny
RASMATAZ
  • MEMBER
The computer doesn't control the OPSU-when the computer energizes the relay for 2secs it primes the fuel system-when vehicle starts up the OPSU powers the fuel pump by closing its contacts by oil pressure.

Check the pressure should be 9-13psi
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Sunday, January 11th, 2009 AT 2:31 PM
Tiny
STUDEBAKER14
  • MEMBER
Hi guys, Just got back inside. Very cold and snowing hard here in Northern Indiana. OK. Fuel pressure (if we read the things correctly) indicates just under 12 psi. I figure that should be enough.

So there is still no 2-3 second prime activity or injector pulse. Remember in my earlier posts, I swapped PCM's with a known working vehicle. Could there be a problem in the wiring harness? Any ideas of where I might start looking? BTW, there is no place in any of the looms that indicate melting or tearaway as if being too close to the exhaust of getting snagged on something. Also remember that she ran fine up to the point where I parked her, then she wouldn't start the next morning. Ans also remember the fluttering fo the FP relay when she DID start, but ran rough.

I'm not the dimmest bulb in the box, but I can't figure this one out. I honestly cannot understand what may be casuing this.

Is there anything under the dash, near the fuse panel that could be unplugged or something?

You guys are great. I am very releived to be able to bounce these troubles off of you. Hopefully, we can figure it out.

CB
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Sunday, January 11th, 2009 AT 8:21 PM
Tiny
RASMATAZ
  • MEMBER
Remove relay from connecor-check wiring for power

At the fuel pump relay wire harness check for power on the orange wire-you should have it-if the fuel pump fuse is okay-

Now turn key to run you should have power on the dark green and white wire let me know-
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Monday, January 12th, 2009 AT 4:36 PM
Tiny
STUDEBAKER14
  • MEMBER
Hi Ras, Orange wire is hot. Fuse is good. With the test light on the Green wire, it does NOT come on with key.

The problem has to be AFTER the key and BEFORE the fuel pump. I've just come in after checking EVERY electrical connection on the engine harness.

Also, all the connections under the dash, on the steering column appear to be intact and undamged.

Keep in mind, I have the insode engine cover off and a test light connected to the green lead so I can see if power is going to the FP. Plus, I can also hear the pump if it is running. It is almost as though there is not enough current to keep the relay engaged. I don't see that as possible as the Amp meter shows a positive charge when it did start, plus there is a high-power battery charger or other vehicle jumping it.
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Monday, January 12th, 2009 AT 5:18 PM
Tiny
RASMATAZ
  • MEMBER
Apply power to the dark green and white wire while relay in place-did the fuel pump come on? If so test the dark green and white wire for an open circuit back to the computer fuel pump relay control
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Monday, January 12th, 2009 AT 6:32 PM
Tiny
STUDEBAKER14
  • MEMBER
Fuel pump does come on when the activation lead (Grn w/Wht tracer) is jumped.

New development. I do not know what happened or what had changed, but for now, the fuel pump relay IS activating properly when the key goes on. It has done this at time during this process, but seems to be fine for now. However, injector are not activating properly.

There have been a couple more incidents when the van will start briefly, then the injectors cease to let the fuel flow. Hence she stalls soon after. Honestly, its like a circuit breaker pops, then comes back on after a while. Yet, the only CB in for the accessory load, (Power windows, locks etc) as far as my understanding.
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Monday, January 12th, 2009 AT 7:21 PM
Tiny
RASMATAZ
  • MEMBER
Test the injector resistances
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Monday, January 12th, 2009 AT 7:31 PM
Tiny
STUDEBAKER14
  • MEMBER
Hi guys, Just back into town from an extended funeral trip for a family member. Just now getting back to the old van. Regarding the resistence across the injectors, they read: 1.6 for the drivers side and 1.3 for the passenger side injectors.

Both injectors open when voltage is applied. Is there a fuel pressure sensor on this vehicle?

FYI: The fuel pump relay "appears" to be operating correctly at this time.

Many thanks,

Chris
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Wednesday, February 11th, 2009 AT 5:29 PM
Tiny
RASMATAZ
  • MEMBER
Is there a fuel pressure sensor on this vehicle?

It doesn't have one
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Wednesday, February 11th, 2009 AT 9:57 PM
Tiny
STUDEBAKER14
  • MEMBER
I guess I'm completely at a loss then and will have to take her in. I simply cannot find what would cause the van to run absolutely normal and not start the next day. Of all the things we have gone through in this forum, there have been no solutions. Obviously, there's something missing.

You guys have been great and I have learned a lot.

Many thanks!
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Thursday, February 12th, 2009 AT 7:11 AM
Tiny
RAMGABE1027
  • MEMBER
It sounds like its an ignition control module problem.
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Wednesday, March 25th, 2009 AT 3:03 AM
Tiny
SFBDBURBAN
  • MEMBER
STUDEBAKER 14

I hope you are still on this site. Did you ever get this resolved? I am having the SAME EXACT problems you were and same symptoms. I wish I could PM you, but I just set up account today and need 10 posts before I'm allowed to PM. Anyways, please let me in on the secret if you figured it out. Thanks.
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Wednesday, May 27th, 2009 AT 4:08 AM

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