84 Cross Injection Help!!!!!

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Sep 22, 2012 | 10:42 PM

rpetrekovich

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4th Gear

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84 Cross Injection Help!!!!!

I am in desperate need of assistance. My car runs great until its hot. The car will not restart until it cools down.

I have found that the injectors do not spray when the car is hot. I have fuel pressure and good spark. I can actually dump a little gas down the throttle bodies while you its hot and the car will fire and the injectors will spray once the engine fires.

I have replaced the fuel pump, the coolant temp sensor, the throttle bodies have been rebuilt (minus replacing the injectors), fuel filter, Ignition switch and new ignition module. I do however feel that even cold, the car is a bit slow to start. The injectors seem to be slow to start to spray. It seems like they are slow to pick up a prime. The injectors however do appear the have a good spray pattern. I would greatly appreciate any guidance.
Thank you!!

Sep 23, 2012 | 08:46 AM

ex-x-fire

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Ohm the injectors hot & cold. At 150* the reading should be 2.2 ohms.
Test for voltage & pulsing ground at the injector connecter.

Last edited by ex-x-fire; Sep 23, 2012 at 08:55 AM.

Sep 24, 2012 | 08:48 AM

Zip Corvettes

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You already found the problem. We work on them all the time and the injectors are usually the cause of most of the issues.

Last edited by Zip Corvettes; Sep 24, 2012 at 08:54 AM.

Oct 3, 2012 | 08:08 PM

rpetrekovich

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I am afraid I need some further assistance.

So I took the advice and replaced the injectors. I deep down felt they had to be the problem before posting. Same situation. Still takes 3 solid cranks of the starter when its cold to start. When its at operating temp, it will not refire. Again, if I drop a little gas down the throttle bodies, the engine fires and the injectors start to spray. I am confused! HELP!!!!

Oct 3, 2012 | 08:39 PM

ex-x-fire

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Who told you to change the injectors? I told you to ohm them.
You need to find out what you don't have when its acting up. No spark, no fuel inj. pulse, or low/no fuel pressure.
Did you set the tps?
You can try putting fresh insulating grease under the ing. module.

Oct 3, 2012 | 11:52 PM

Tom400CFI

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From: Park City Utah

Quote:

Originally Posted by rpetrekovich

takes 3 solid cranks of the starter when its cold to start. When its at operating temp, it will not refire. Again, if I drop a little gas down the throttle bodies, the engine fires and the injectors start to spray. I am confused! HELP!!!!

Fuel pump relay. When you're cold, it "takes 3 solid cranks of the starter...to start".

Then hot, you're getting no fuel from injectors UNTIL you pour some gas to fire it up....then it sustains itself. Oil pressure. The car has a fuel pump relay to energize the fuel pump circuit, AND a oil pressure switch -when you build oil pressure, that swtich closes and sends power to your fuel pump also -"backing up" your fuel pump relay circuit. I think your fuel pump relay is faulty, or signal to it to energize it, is not functioning. I think that you're only getting a fire, after you've build the 4PSI required to close that oil pressure switch and kick your fuel pump on.

I'm sorry that a vendor encouraged you to buy injectors. In fact, in a CFI car, they are very RARELY the cause of issues.

Going forward, see if there is a correlation between oil pressure and injectors supplying fuel. Do you hear the fuel pump run for ~2 seconds when you initially turn the key on? If yes on the first and no on the second, diagnose the fuel pump relay circuit.

Last edited by Tom400CFI; Oct 4, 2012 at 12:00 AM.

Oct 5, 2012 | 11:50 PM

rpetrekovich

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Okay I have done some additional testing.
1. Testing the injectors. 1.3 ohms cold, 16 ohms hot.
2. I had previously tested fuel pressure, and I have 13 pounds. Honestly, I never thought to test the pressure after it was hot. After testing hot, no fuel pressure.
3. The oil pressure is great.
4. I mentioned previously that I replaced the coolant temp sensor. I replaced it with a new two wire. I did just find that my cooling fan is no longer kicking on. The fan did previously operate prior to the sensor replacement. I have no idea if this has any relationship to the fuel problem, but I wanted to throw it out there in case it is relevant.

I will pick up a fuel relay tomorrow and see what happens. Let me know if the info helps identify the problem. And thanks for all of the help and input!

Oct 6, 2012 | 08:19 AM

ex-x-fire

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If you suspect that you have a problem with the oil pressure switch (thats in the fuel pump wiring diagram), they had early & late 84 model year switches. My early 84 had a bad one that caused the pump to run even when the key was in my pocket.