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TBI isnt getting fuel during first 5 sec of turn over...

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rastaangel

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Ever since I went and picked up my '88 truck a month ago it has always hesitated on start up... It will always start but sometimes it takes 5-8 seconds of cranking to get it to start.
I just had another guy in my building crank it over while I watched the injector pods and its not getting fuel when its turned over for that 5-8 seconds then it gets fuel and starts and runs fine.
I know the pump works cuz I can hear it humming and I just replaced the fuel filter. If it makes a difference my fuel pump is wired into a toggle switch on my dash cuz the OEM selector switch was gone and the tank selector valve was filling the other tank while the truck was running so the tank selector valve has been bypassed and the fuel pump is on a 12v toggle on my dash
What could be causing this hesitation? Possibly a pressure regulator?
 
Lack of oil pressure? Engine needs to build pressure before the ECM will fire the injectors?

If you shut it off, it fires immediately. Mine does this exact same thing.
 
No its got awesome oil pressue, it almost pegs out the oil pressure gauge when I turn it over
 
Fuel pump might be weak...check the pressure with a gauge at the fitting on the fuel rail...my friends 2001 Chevy had been taking a long time to get fuel and fire up in the mornings lately,he'd have to play with the gas pedal and spin it over quite awhile before it would fire up...but once started and driven,it'd start instantly all day long...he checked the pressure and it was only 37 lbs,he decided to replace the pump before it stranded him somewhere,it was supposed to have 55 psi..he pulled the bed off and slid it back to change the pump rather than drop the tank,he had the bed off it not long ago, so it came off easily in about 20 minutes...

It could be the oil pump switch too,I know of no way to test one other than replacing it to see if it made any difference..also there is a "5 second prime curcuit" that has to function for it to start like it should within a few revolutions,google that and you'll probably find more info on it..
I have seen a lot of GM vehicles with bad power wires or connections to the plug at the sending unit cause voltage drop and these kinds of troubles too...
 
Gauge sending unit and ECM switch are different. Gauge sending unit is at the filter. ECM switch is at the top of the block in the back. Delayed pressure after the truck sits.
 
I'm interested in the resolve to this as well. Mine has done this since I've owned it. Fuel pump was failing when I bought it and was replaced along with the EGR valve, battery, and spark plugs. If I crank it a couple/few times, stop, then crank again it fires right up. If I just let it crank (for the first start of the day) it takes a lot longer. Mine is also an 88 with the stock 350.
 
Just to prove it, unplug the switch wires. Jumper wire between them. Then start it. See if is different.
 
I may have found my issue!
I googled the "5 second fuel prime circut" and found another forum with the same issue and it said to check the ECM A and ECM B fuses, check the fuel relay, and check the relay wire to the ECM.
I went to walmart and bought a new fuel pump relay just to eliminate that. So I changed the relay and checked the relay/ECM wire and it was good. Then I checked my fuse box and my ECM B fuse was blown, so I changed it and it insantly blew. So I pulled my fuse box off and found the wire for that fuse was pinched and the wire coat was worn threw and it was grounding out and blowing the fuse so I fixed that. Now my truck starts far better! I know it would anyways since it was already running but the fuse didnt blow so that might be it. I parked the truck and ill try to start it tomorrow and see how well it starts and report back
 
Or you could have looked in Injection Section at the wiring diagram?

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I hope so. I assumed you had checked those. My bad. I forget that not everybody has been working on these truck from when they were first available.

Let is know what happens with it.
 
Look at the diagram! If you want faster starts remove the oil pressure switch!

I like it as is, lets the engine get some oil flowing before fired up.
 
That's what my jumping it does. I would never run it that way. I like that the engine shuts down if I'm not paying attention.
 
ktmoutfront said:
That's what my jumping it does. I would never run it that way. I like that the engine shuts down if I'm not paying attention.
Click to expand...

If the fuel pump relay is working, your engine will not shut down for low oil pressure. The oil pressure switch and relay are connected in parallel. This is why the OP had delayed starting when the ECMB fuse which powers the fuel pump relay control circuit was blown, the pump didn't start running until the engine made oil pressure.

It wouldn't be hard to make it work this way by running the switch and relay in series though, just would have extended crank times on every start.
 
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