1990 Suburban 5.7 Tbi Extended Crank Problem

[semiunmarked]

Jump into the wayback machine Mr Sherman and see if you can help me out..............

 

I have a 90 Suburban with the 5.7 L TBI. The engine will crank for 15-20 seconds - the oil pressure gauge will jump up - the check engine light flashes twice and it will then start right up. Does this everytime.

 

Suggestions?

[ChevyTech007]

Possible fuel pump relay. The relay should turn the fuel pump on for 2 seconds when the key is turned on. The oil pressure sending unit powers the fuel pump after that so that if you loose oil pressure it will shut the engine off. Sounds like you are not getting the 2 second prime.

[semiunmarked]

I should have mentioned that I replaced fuel pump relay, fuel filter, O2 sensor, complete tune up, etc.

It's a very unique problem and has many heads scratching

Keep the suggestions coming..........

[luminaapv3]

quick question, are you going from the off position straight to the run position?

If so try this, go from off position to on position, pause for a couple of second, then crank the engine. My truck sort of does the same thing, but if I pause a couple of seconds to let the fuel pressure build it starts without hesitation.

I just assumed that it needed that 2 seconds to prime the system since it has the automatic fuel pressure release mechanism built into the fuel regulator.

Anyways give it a try and let me know if it does the same thing.

[lucky13]

I wish i had a extended crank

would make my wife really happy

[semiunmarked]

quick question, are you going from the off position straight to the run position?

If so try this, go from off position to on position, pause for a couple of second, then crank the engine. My truck sort of does the same thing, but if I pause a couple of seconds to let the fuel pressure build it starts without hesitation.

I just assumed that it needed that 2 seconds to prime the system since it has the automatic fuel pressure release mechanism built into the fuel regulator.

Anyways give it a try and let me know if it does the same thing.

 

No change - can hear fuel pump in tank when key is in 'on' position.

 

Cranks 15-20 seconds - check engine light flashes twice - starts right up. My poor starter............

[gibbons948]

only thing i can think of is the throttle bodies can actually leak from the top causing it to partially flood for the begining of the crank cycle.worth checking out.

[luminaapv3]

How's your oil pressure? As ChevyTech007 said, it runs the fuel pump after. Just a place to start.

[semiunmarked]

Problem solved - apparently the previous owner was a card carrying member of the duct tape & hacker club.

 

Removed the tape and wire loom from the wires leading to the fuel pump relay - all the wires had a portion of wire peeled back (they were all taped together without taping each wire individually) and the gray wire was cut. This gray wire feeds the fuel pump and is inline with the oil pressure sensor. Mr Hacker tied this cut gray wire to the positive 12V source at the map sensor! The butt connector had failed. After reconnecting the wires properly, taping them up and replacing a blown ecm fuse the problem was fixed.

 

Lesson: never assume and don't be afraid to dig a little.

 

Thanks for all the suggestions........