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Old 07-28-2013, 09:48 AM
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1990 tbi problem

I was ask to look at a 90 Chevy C60 with a 366. It will not start unless you use some starting fluid. then it will run ok. They have replaced fuel pump,distributer, temp sender and i replaced fuel regulator part i think it is a stander pr152 . I pluged fuel return line and it started. So i replaced regulater diaphram but it steal wont start. I removed tbi and found out that the regulater would leaked at very low presser like the seat is bad. I need some advice so as not to have to keep throwing money at it trying to get lucky and fix it. Thanks Doug

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Old 07-28-2013, 10:18 AM
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What is the cranking fuel pressure. You should see a mist of fuel while cranking coming out of the injectors. The fact that if you block off the return it starts makes it sound like either the regulator is not working or the fuel pressure is to low with the lower cranking voltage. I would look at the wiring to the pump to check for corrosion which could lower the voltage to the pump and reduce pressure. Remember you have 14V while running but only 10-11 while cranking.
I have seen the ground corrode near the right hand side of the fire wall that is used for the injector ground. In a truck that old I would bet on a bad electrical connection somewhere. Check the pump ground as well. It is usually bolted to the frame somewhere.
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Old 07-28-2013, 10:30 AM
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It is spraying gas from the injectors as it is cranking. I dont have a gauge. it has a saddle tank and you can hear pump runing. It sounds strong but it could be low voltage. If regulater was bad presser would be low? Can you put a gauge on just the pump? Is this pump made to run full time when key is on?
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Old 07-28-2013, 10:59 AM
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I agree with chet. Sounds like a ground issue. At the passenger side rear of the engine there is a ground that bolts from the engine to the frame. I have seen those completley deteriorated (broken in two) from years of exhaust heat as they are next to the exhaust manifold. If that ground goes bad, because it grounds the frame , it will cause a pump to run too slow and not create enough pressure. The pump ground is on the drivers side frame back behind the rear wheel.
Check and clean both grounds.Then re test.
Last one I had...the engine would shut off when the running lights were turned on. A deteriorated / missing ground at the engine to frame was the culprit
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Old 07-28-2013, 10:59 AM
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Quote:
Originally Posted by Old Doug View Post
It is spraying gas from the injectors as it is cranking. I dont have a gauge. it has a saddle tank and you can hear pump runing. It sounds strong but it could be low voltage. If regulater was bad presser would be low? Can you put a gauge on just the pump? Is this pump made to run full time when key is on?
So it is spraying fuel but wont start yet if you spray fuel in it it starts or if you block off the return it starts, this makes no sense. Are you spraying fuel or starting ether. If it is ether it could be a weak ignition while cranking as well again due to lower cranking voltages. The ether lights off much easier that fuel.

If you are using either to start it, dont, it is giving you false troubleshooting information. A squirt bottle of gas is a better test solution. Be careful with whatever you use.
If the regulator was bad pressure would be low, that is correct.
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Old 07-28-2013, 11:27 AM
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Sorry i have not been useing starting fluid i have used carb cleaner and gas. It looks to have a hot spark. I will check ground on pump but it sounds good. I had a 2.5 buick that would spray fuel from the tbi and not start i replaced the computer and it started. I removed the tbi on this truck and blow on the inlet side while blocking the return side with my finger and you could tell it didnt hold 100%. I took it apart and held the regulater down and it did the same. The spring looks good. Before i stop working on it sat i put a washer under the spring and it started by its self . I ate lunch and tryed it agin and it started.
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Old 07-29-2013, 11:37 AM
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I looked at ground and every thing looks good it started today on its own . I think it needs a new TB . Either the spring is weak or the seat is worn becauce more spring presser is makeing it work. I am going to leave it like this and see what happens. Time will tell.
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Old 07-29-2013, 03:02 PM
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Makes sense to do it that way. Thanks for posting the feedback. That helps anyone else who has the same problem.
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Old 07-29-2013, 05:34 PM
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Bad news. I started it several times and it seamed ok so i took it for a drive about 5 miles at 50MPH@ 4500Rpms very low geared. It ran good but when i got back and turned it off it wouldnt start. I let it seat about 5 miniutes it started up but it would not start every time. It was raining so i didnt check it out.
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Old 07-30-2013, 05:03 PM
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Today i took my starter button with me and found out that it would start every time with it. If it wouldnt start of the switch it would with the button. A buddy called me after i had come home and said that he know of a truck like this one that had a starter button added to it because of it not starting . As we were talking he rememberd a truck that had this problem do to a oilpress switch. It makes sense why it would not start after it got warmed up. Tomorrow i will check it out.
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Old 07-31-2013, 04:41 PM
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Today i checked oil presser with a gauge and it was good so i checked sending unit and it check out ok. The owner told me yesterday he would be ok with a starter switch so i instald a button in the dash to start it with. Not the greatest deal but it seams to work. I would like to have found the problem but it is runing and starting for now. Thanks to every one that tryed to help.
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Old 07-31-2013, 04:55 PM
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Sounds like a bad ignition switch.Have the same problem on a 94 GMC.Sometimes the switch is not supplying a full 12 volts.Drives the ECM crazy.It can cause some weird problems & have you chasing your tail.
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Old 07-31-2013, 05:37 PM
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I check voltage on switch input and out put and at every thing that has power to it and it had same voltage with ignition switch or push button. Also checked grounds. I hate to by a new switch and not fix it they have spent several dollars and got no were. If they didnt like the button i would try a new switch.
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Old 07-31-2013, 05:42 PM
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My switch was $14. Kinda pain to replace.Had to drop the steering column,but'haven't had a problem since.I still have wires ran for the button tho.Just in case.LOL.
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Old 07-31-2013, 05:47 PM
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Thats not bad for a switch. If i ever work on it agin i will put a new switch in it just to see.
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