TBI crank and no/delayed start

[RichLo]

New problem has me cornfuzed. 1993 k1500 5-speed. Cranks and cranks then fires off and runs great once its running. Both injectors firing Christmas tree patterns when cranking. New ICM two years ago along with new cap/rotor/wires/plugs. New fuel pump 6 years ago (5000miles?) Along with fuel filter, new tank and full TBI rebuild at that time.

Problem popped out of nowhere this summer. It just started to take FOREVER to fire off and run. It doesn't matter on how long the fuel pump primes before cranking or if the throttle blades are open or closed.

I don't want to throw parts at it, any help is appreciated!

Thanks!

 

[PlayingWithTBI]

Did you check your fuel pressure? Low pressure = hard starts. How about your coil, when was it replaced last? There's a lot of guys who had worse luck with their ICM and possibly a bad coil will take it out? Maybe weak spark (got an HEI spark tester)? Once you get the engine running, try spraying some water on your coil, see if it stumbles. Take a look at your cap and rotor for signs of deterioration.

I know you've seen a lot of similar threads, I'm just throwing out something to see if it sticks.

 

[RichLo]

Thank you! Some things to try when I get time. I'll let you know when I find the problem.

 

[Schurkey]

The fuel pump IS priming? Fuel pressure is good DURING cranking?

Fuel spray during cranking? How old is the gasoline? Any chance you've got some water in the bottom of the tank?

Have you checked for spark? A weak pickup coil may not trigger the module properly at low (cranking) rpm, but pickup coil signal gets stronger with RPM. 'Course, if the pickup coil isn't triggering the module, you shouldn't have fuel spray, either.

 

[RichLo]

So, I ended up throwing a few parts at it but finally found the problem. The fuel pump relay. It's weird that it would run just fine and just had a problem starting.

Also replaced the ICM and TPS before the relay. It seems to rev quicker and run happier now though so maybe one or both of those were going bad also.

 

[someotherguy]

So, I ended up throwing a few parts at it but finally found the problem. The fuel pump relay. It's weird that it would run just fine and just had a problem starting.

Also replaced the ICM and TPS before the relay. It seems to rev quicker and run happier now though so maybe one or both of those were going bad also.

Not weird at all. The fuel pump has a redundant circuit through the oil pressure switch. That's why it would fire up after you cranked it long enough to build minimum oil pressure for the switch to close and power the fuel pump.

Now if your oil pressure switch coincidentally had gone bad as well, then you'd have a complete no-start condition.

Richard