96 7.4l Vortec No Start, Hard Start, does start, but then dies after 10 min

[Chopkraf]

All,
I have a 96 7.4l Vortec that has some running issues. I will list what I have replaced and tested: New Fuel Pump, lines, Fuel Tank, Fuel Filter(tested the fuel psi...I was getting 60 psi), Ignition Control Module, Ignition Coil, New Distributor (Cap, rotor, and body(old distributor rotor was spinning)), Crank Shaft Sensor, Spark Plugs (gap is correct), Spark Plug Wires, and EGR. I placed the engine at TDC and lined the new distributor rotor to the stamped 8 on the body. The truck acts like it wants to start, and about after the 5th to 6th try it will start and run...After about 8 minutes, it begins to sputter and finally die. Im really scratching my head on this one, so any help would be appreciated.

Chuck

 

[Christian Steffen]

Is it throwing any codes while running? How many miles are on the truck? Did this problem start all of a sudden or is it something that has slowly started being an issue?

 

[Chopkraf]

Is it throwing any codes while running? How many miles are on the truck? Did this problem start all of a sudden or is it something that has slowly started being an issue?

I was pulling a camper up hill, and lost all power...it threw P1192, P0700, and a P0137. After I replaced the parts above, I have not see these codes again. The truck has 150k on it.
Thanks,
Chuck

 

[someotherguy]

Next time it chugs out and dies, check the fuel pump relay. If it's burn-your-fingers hot, then you've found a problem. May not be THE problem, but it's not helping.

A beat-up old '98 7.4 I had acted somewhat similar, especially the crapping out after it had been running a while. The relay was crazy hot. They tend to melt the socket area around them and cook the pins, too. If you find this to be happening you could try a new relay, but I'd also squirt some good quality contact cleaner down in the socket. (I like DeOxit; good stuff.)

Now don't get me wrong; it's normal for the relay to be uncomfortably hot - but there's degrees (pun kinda intended), ya know?

Some Vortec trucks that have cooked the relay socket would do well to wire a new socket underneath the electrical center, with the wires firmly soldered to the new one instead of simply crimped. This is a problem area on many of those trucks, small or big block.

Richard

 

[Christian Steffen]

So you haven't replaced injectors then? Hook up your fuel pressure gauge and see if the pressure is bleeding down when the pump shuts off, although I doubt those are causing it to die.

Did you check the cmp retard after replacing the distributor?

 

[Chopkraf]

So you haven't replaced injectors then? Hook up your fuel pressure gauge and see if the pressure is bleeding down when the pump shuts off, although I doubt those are causing it to die.

Did you check the cmp retard after replacing the distributor?

I did check the retard and no matter how i many times I think I set it SparkAdv says -25 degress...I know Im at TDC (i had a buddy with a compression gauge watch it while I turned the balancer), and I have lined up the rotor to the 8, but the damn thing still reads -25(Im using an ODB II scanner from Harbor Freight).

 

[Chopkraf]

Next time it chugs out and dies, check the fuel pump relay. If it's burn-your-fingers hot, then you've found a problem. May not be THE problem, but it's not helping.

A beat-up old '98 7.4 I had acted somewhat similar, especially the crapping out after it had been running a while. The relay was crazy hot. They tend to melt the socket area around them and cook the pins, too. If you find this to be happening you could try a new relay, but I'd also squirt some good quality contact cleaner down in the socket. (I like DeOxit; good stuff.)

Now don't get me wrong; it's normal for the relay to be uncomfortably hot - but there's degrees (pun kinda intended), ya know?

Some Vortec trucks that have cooked the relay socket would do well to wire a new socket underneath the electrical center, with the wires firmly soldered to the new one instead of simply crimped. This is a problem area on many of those trucks, small or big block.

Richard

Ill take a look at that today, and report back.

Thanks,
Chuck

 

[Christian Steffen]

I did check the retard and no matter how i many times I think I set it SparkAdv says -25 degress...I know Im at TDC (i had a buddy with a compression gauge watch it while I turned the balancer), and I have lined up the rotor to the 8, but the damn thing still reads -25(Im using an ODB II scanner from Harbor Freight).

-25? Damn, the spec calls for +/- 2* on the cmp retard.

read part 2 of this article.

http://www.gmtruckcentral.com/articles/distributor.html

 

[someotherguy]

What you're using to read it with may not be capable of reading the cam retard. Spark advance is not the same thing.

Last few I did I had a borrowed OTC Genesys; there are some cheaper scanners that can do it like some of the AutoXray stuff.

Richard

 

[Christian Steffen]

What you're using to read it with may not be capable of reading the cam retard. Spark advance is not the same thing.

Last few I did I had a borrowed OTC Genesys; there are some cheaper scanners that can do it like some of the AutoXray stuff.

Richard

I didn't even catch that he said spark advance.

If you get the app car gauge pro with the correct Bluetooth adapter you can read cmp retard. Otherwise you could also drag it to a shop that has a tech II scanner and have them do it.