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Old 10-22-2004, 06:03 PM
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TBI fuel injector delay???

I have an 87 TBI 350 truck when i try to start it, it takes 2 or 3 times to start ive found that the injectors arent fireing right away the fuel pump is coming on and is getting the right pressure just the ECM seems to be delaying the start for some reason. from what i know about this ecm it doesnt need to see oil presure to start but even if it did it is geting oil presure so i still dont understand it. Anyone got any ideas??

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Old 10-22-2004, 06:22 PM
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Fuel Injector

Sounds like you are not getting the fuel pump prime. Does the pump come on for a few seconds when you first turn on the key? If it does then you have a stuck check ball inside the pump or a leaking hose inside the tank. If it is the checkball, Sometimes you can disconnect the fuel line and blow compressed air in the line to re-seat the ball.
As far as the injectors...Every time the coil fires so do the injectors. The computer just delays the amount of time to deliver the correct amount of fuel. If all of this checks out then run the codes on the computer and repost. Good Luck.
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Old 10-23-2004, 02:12 AM
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Air

Doc here

Locate the shrader valve and CAREFULLY blow off the air in the fuel lines... That is probably what is causing the delay...

The reference pulse from the Distributer is also the clock pulse that sets up the computer for signal timing on the computer controlled devices like the fuel infectors..<---misspell, but I like it so it stays)So when it fires, the injectors should fire also with no delay (larger than a millisecond..)

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Old 10-23-2004, 10:11 PM
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Have you actually checked the psi,or are you assuming that the psi is ok if you hear the pump? The is no shreader valve on these models, you have to open the fuel system to install the tester. 11-13 psi is specs for Gm TBI.

The oil pressure switch contains a back up for the fuel pump relay. If the pump relay fails, the back up will allow the fuel pump to run once you get enough oil psi.

Check that fuel psi. The easiest place I have found to do it is at the filter. (put a new one in while you are down there.)
The filter is under the truck, but in my experience, the tester is easier to install there than at the back of the tbi unit.
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