Question about 1994 GMC Sierra

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94 sierra won't start. I would like to check fuel pump pressure at the injector body. Should there be enough pressure to squirt fuel when the ignition is turned on? TKS

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There should be enough pressure to squirt fuel if you have a test point. The injector will not spray untill it sees a pulse from the ignition module. You might have someone turn the ignition switch on while you listen at the tank, the pump should run for two seconds. If not I would start with the relay, maybe swap it with the a/c relay, should be same part #. if the pump does not run, sometimes a sharp rap to the bottom of the tank will dislodge a stuck pump(only temp. Not a solution)but will let you know if the pump is the problem. If the pump runs and you have pressure but still have no spray at the injector then you need to look at ignition module, crank sensor. Depending on if you have fire at the plugs. If you have no fire, the crank sensor is suspect. If there is fire check the ignition module. If you take the ignition module to an auto parts store(i.e. Advance, O'reilly ) they have a tester to tell you if it's bad. Hope this helps you find your problem.

Posted on Nov 17, 2009

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I wouldn't do it that way, with static electricity, and voltage going to those sensors, you could cause a fire or an explosion, just because there is fuel shooting out, it doesn't mean the pump is putting out what it should. The safest way, and what the pressure is,is to have a fuel pressure test done, or buy a fuel pressure tester and do it yourself.
You can purchase them at an auto parts store. Some are expensive.

Posted on Nov 17, 2009

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Yes there should be enough pressure to squirt when the key is on.you should have about 10-15 psi of pressure at that port. another way to tell if your fuel pump is not working open the gas door remove the gas cap and put your ear to the fill port and have some one turn the key on, if you don't hear a buzz than the pump isn't working.

Posted on Nov 17, 2009

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I have the same problem but i spray starting fluid in and it starts but wont without it whats wrong

Posted on Nov 29, 2009

  • richardwight Nov 29, 2009

    ITS A1995 CHEVY silverado has a new fuel pump new sensors new fuel filter but will only start if primed onces running will stay running but if you turn it off wont start on its own help

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Your fuel pressure should show around 50 psi with key on. Is it?
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I have a 1989 GMC sierra 4.3 Liter, fuel pressure


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1 Answer

Started ran for awhile then died an wont start


Start with the simple and replace your fuel filter, a dirty filter can cause your engine from starting. At worst, your fuel pump has failed and will need to be replaced. Before replacing the fuel pump, inspect all the fuses and wire leads from the fuel pump harness. Note: that the ground wire is separately grounded at the frame, so inspect that for any damage due to corrosion.

You need 3 things.
Compression
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure. 63-64 lbs.
If you have all 3 then move on to injector pulse to all injectors. I think each injector is on a seperate driver on that one. Check for pulse to all of them.

You may be weak on fuel pressure, even a couple of lbs low on a cold start will cause a no start. Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems. One test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem.
Run the full fuel pressure test, here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure. Later V6 and V8 gm engines should have 60-66 fuel pressure.
* Cold start should be 64-65 lbs of pressure. If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
* Engine running should be 60-66 lbs pressure depending on engine load.
* Full pressure with return pinched off should be 75-85 or more. and if it has a fast leak down after shut off you have a leak.

The 75-85 is only a check on the capable full pressure of fuel pump. If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.

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2 Answers

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