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I have a 1992 Pontiac Sunbird with a 3.1, automatic. I have replaced the motor, timing chain, trans pan and gasket, drained all gas and refilled with new gas, new plugs and wires, new coil packs, base coil pack mount, new fuel filter, and sensors, new fuel injectors. It has great compression, spark, and great fuel pressure.

I can shoot starting fluid directly into the fuel intake and it will run as long as it is receiving the starting fluid, but it will not run on its own. I have also gotten the car to semi-start for only a second. Then it could take as long as an hour to make it do it again.

  • could the lack of a ground strap from motor to frame keep car from starting? – Curtis Mar 7 '17 at 1:18
  • Have you checked fuel pressure? Could he the fuel pump isn't working. It's definitely a few problem if it will start on starting fluid. – Pᴀᴜʟsᴛᴇʀ2 Mar 7 '17 at 2:26
  • first check your codes. try a noid light to see if your injectors are firing (your auto store should have them for rent) – agentp Mar 7 '17 at 3:48
  • You say the fuel pressure is good, but have you checked the injectors / injector pipes to see if fuel is being delivered? – Solar Mike Mar 7 '17 at 8:02
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    But the pump engaging doesn't mean fuel is being delivered, it just means the pump is running. You checked the pressure at the rail it sounds like so the rail is making fuel available. One way to test whether the injectors are actually firing is to measure the current they draw. A clamping AC current probe for an oscilloscope will tell you. Or, replace the fuse for the injectors with a piece of wire and put the clamping AC current probe on that. Since you're looking for a wave form you can't do this easily with just a DVM – cdunn Mar 13 '17 at 16:31
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If you can get this engine to run fine for a bit with starting fluid then you have a problem isolated to the fuel delivery:

Not in the best logical order, but from easiest to hardest to check =)

  1. Fuel Pressure: What is the fuel pressure? (Hack: Does fuel squirt out of the fuel rail valve when the key is turned on?) 30 to 40 ish is good ... check your specs.
  2. Interference: Is there air in the fuel rail. Since you recently replaced this engine, things were disconnected for a while. Sometimes there is an air bubble in there. Bleed it out at the valve, pressure regulator, or return line.
  3. Fuel Volume: What is the fuel delivery rate? Does the volume match the spec for your engine? (Hack: How long does it take to fill up half of a soda bottle? 15 seconds or less ish? ... look up your spec)
  4. Pressure Regulator: Is the fuel pressure regulator leaking or faulty? It may have sat for an extended period exposed. This is a common fault and cheap to fix. (Hack: Does it smell like gas?)
  5. Vacuum Leaks: Intake manifold or vacuum leaks? When the engine runs with starting fluid, is it smooth and normal-ish. (Hack: Does the engine start or "sputter some" when the starting fluid is sprayed around the intake manifold but NOT in the air intake?)
  6. Injector Signal: Are the injectors getting signal? Do they have an electrical signal going to them?
  7. Injectors: If the fuel pressure is all good, I would say check injectors ... but you have new ones. Double check they gave you the right part number.
  8. Sensors: If you have good spark (coil packs are a common fault, but you have new ...) and good fuel pressure but not injector pulse, check sensors and connections. Start with MAF sensor ... unplug it for a bit and see if it runs in "limp" mode. Check EGR and other sensors. Unplug connections, clean, look for debris, etc...
  9. Hmmm: Try other sensors, but a problem here would lead into more complicated diagnosis with advanced equipment ...

Good luck. I'd love to know how it turns out =)

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I would most definitely tear down the upper plenum and clean out the fuel ports. They tend to get clogged and can not recieve fuel.

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    Welcome to the site. We appreciate you being here and your contributions. Please be aware Stack Exchange doesn't work like a forum. We are a Q&A site which tries to rely on fully finished answers backed up by references. Answers such as this, while possibly being accurate, only tell part of the story. To better answer it, please provide why you believe this to be the issue, how to diagnose it as the issue, and then how to fix the issue. Answers which are logically thought out and providing detailed how-to's on fixing the issue are usually well received. – Pᴀᴜʟsᴛᴇʀ2 Mar 7 '17 at 14:32
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Sounds to me like you have a fuel delivery problem, if it runs with starter fluid then the injectors are working and ignition is fine.

I would check the main fuel line going to the fuel rail, you may have pressure but may have insufficient volume. Also, make sure the new fuel filter is not installed backwards.

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    how do you conclude the injectors are working from running on starter fluid? – agentp Apr 7 '17 at 22:10
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I had a GMC with 4.3 Vortec ; similar problem - I had to put fuel into the manifold to start it but then it ran all day. The dealer did not know what it was so he replaced everything in the fuel system under warrentee . So , not much help except it was something in the fuel system.

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  • The truck was a 1992 and this happened in 1994 before it had 50,000 miles. – blacksmith37 Feb 1 '18 at 17:00
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Check the MAF sensor (actually look at the data comming back from the computer and see what is missing). If the MAF sensor is telling the computer no air is getting into the motor - then the computer cuts the fuel. Some GM cars have an override. To test the MAF sensor issue, simply unplug it. Computer should go into speed density mode - run rough, but run.

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