94 chevy c1500 5.7L TBI K code fuel, spark no start.

History: Original owner 94 c1500 5.7L TBI K code engine 164K mi. She stopped in the driveway about two weeks ago, and hasn't started since, the stop was abrupt, no strange noises engine just stopped which led me to believe it might be electrical, but who knows. Original distributor, AC Delco ICM, AC Delco plugs (black), wires, cap, and rotor after market, new O2 sensor, replaced idle control valve with aftermarket about a year ago, besides duals exhausts sound system she's stock. Low compression in #1 (55 lbs), #3 (90, 70, 40 lbs), #5 (90 lbs), haven't checked the others yet but that was enough to let me know something is wrong that I don't understand oh yeah I checked the fuses under the dash, is there any ignition fuses somewhere else.
Been reading a little bit, and I am asking if the timing chain can cause this issue, by having too much slack, and not allowing the cam to open and close valves in the right timing, or the pistons are not rising and falling correctly. Give me some feedback, because I don't really want to be gutted by paying for troubleshooting labor.
Little Help

shipahoy said:

History: Original owner 94 c1500 5.7L TBI K code engine 164K mi. She stopped in the driveway about two weeks ago, and hasn't started since, the stop was abrupt, no strange noises engine just stopped which led me to believe it might be electrical, but who knows. Original distributor, AC Delco ICM, AC Delco plugs (black), wires, cap, and rotor after market, new O2 sensor, replaced idle control valve with aftermarket about a year ago, besides duals exhausts sound system she's stock. Low compression in #1 (55 lbs), #3 (90, 70, 40 lbs), #5 (90 lbs), haven't checked the others yet but that was enough to let me know something is wrong that I don't understand oh yeah I checked the fuses under the dash, is there any ignition fuses somewhere else.
Been reading a little bit, and I am asking if the timing chain can cause this issue, by having too much slack, and not allowing the cam to open and close valves in the right timing, or the pistons are not rising and falling correctly. Give me some feedback, because I don't really want to be gutted by paying for troubleshooting

Click to expand...

Relax.
It is most likely an electrical problem.
No offence my freind but I dont think that you should go head first into compression testing.
Forget all about compression testing.
******* calm down and relax bud.
i am here for you just like the people on this forum were here for me.

Compression readings are TERRIBLE.

Describe your process for compression testing, starting with whether you blocked the throttle at least part-way open.

DO YOU HAVE SPARK AT THE SPARK PLUGS WHEN CRANKING THE ENGINE?

DO YOU HAVE FUEL SPRAYING FROM THE INJECTORS WHEN CRANKING THE ENGINE?

thinger2 said:

Relax.
It is most likely an electrical problem.
No offence my freind but I dont think that you should go head first into compression testing.
Forget all about compression testing.
******* calm down and relax bud.
i am here for you just like the people on this forum were here for me.

Click to expand...

OK, I'm relaxed, now what do I do, and what do I look for, and where? Thank You.

Schurkey said:

Compression readings are TERRIBLE.

Describe your process for compression testing, starting with whether you blocked the throttle at least part-way open.

DO YOU HAVE SPARK AT THE SPARK PLUGS WHEN CRANKING THE ENGINE?

DO YOU HAVE FUEL SPRAYING FROM THE INJECTORS WHEN CRANKING THE ENGINE?

Click to expand...

No did not block the throttle.
No spark disconnected the coil.
Yes, fuel is spraying from injectors when cranking. Thanks.

shipahoy said:

No did not block the throttle.

Click to expand...

Compression readings should increase when the engine can ingest more air.

Whether the readings increase from "terrible" to "acceptable" is yet to be determined.

shipahoy said:

No spark disconnected the coil.

Click to expand...

No spark BECAUSE you disconnected the coil? Reconnect the coil, see what happens.

Make sure you have power to the red wires at the coil when the key is turned to "Run".

shipahoy said:

Yes, fuel is spraying from injectors when cranking.

Click to expand...

Tells me the computer is getting an RPM signal. That's good news.

Hi Forum, Got the old 94 running, it appears that it is not holding fuel pressure. Primed fuel pump, fuel pressure tested at 12 psi, but when the relay switch makes a click the pressure drops down to 0. Done this three to four times and it is always the same, when the relay switch makes a click the pressure drops down to 0.

The engine will only start when I prime it, and will run at 0 fuel pressure, because when the relay switch clicks the pressure drops to 0, but runs, not good, but runs like starving, but when revved up sounds good, in idle not so good.


I removed the relay switch it is 30 years old, and GM AC Delco discontinued the OEM. Is Standard a good choice?
Is there anyway I can check the relay switch before buying a new one?
Is there any other systems between the fuel pump and the relay switch, that I should check?

shipahoy said:

Primed fuel pump, fuel pressure tested at 12 psi, but when the relay switch makes a click the pressure drops down to 0. Done this three to four times and it is always the same, when the relay switch makes a click the pressure drops down to 0.

Click to expand...

That's normal, when you turn the Key On Engine Off, the ECM/PCM will "Prime" the system for 2 seconds then shut off. There's no check valve in the line so, pressure will go to zero almost immediately. You need to check if the fuel pump comes on when cranking.

PlayingWithTBI said:

That's normal, when you turn the Key On Engine Off, the ECM/PCM will "Prime" the system for 2 seconds then shut off. There's no check valve in the line so, pressure will go to zero almost immediately. You need to check if the fuel pump comes on when cranking.

Click to expand...

The truck will start when I prime it, and I let the truck run for about 30 minutes every time, but to get it started I have to prime it even when the injectors are spraying, and they continue to spray while running. Doesn't that mean the fuel pump is working if it keeps running?
Can there be something wrong with the TBI system, it's all over 30 years old, I know during idle my injectors have some dripping mixed with spraying when idling, but when I rev it up I get a good solid spray and a smoother running engine?

shipahoy said:

The truck will start when I prime it, and I let the truck run for about 30 minutes every time, but to get it started I have to prime it even when the injectors are spraying, and they continue to spray while running. Doesn't that mean the fuel pump is working if it keeps running?

...Is there any other systems between the fuel pump and the relay switch, that I should check?

Click to expand...

Greetings shipahoy,

Having to prime your system in order to get the truck to start could be explained by an out of spec (too low)
fuel pressure sitting at the input to the TBI injectors. As a matter of fact I searched for the phrase 'hard starting'
in the 1994 Driveability, Emissions, & Electrical Diagnosis FSM, and ended up with this:



In English, your injectors are spraying, but they aren't spraying enough, but once you add a little more
fuel, it will run. So in order to troubleshoot this further, you are going to need to check the fuel pressure
with an accurate gauge in order to prove/disprove this theory. NOTE: If you don't have this kind of test
equipment, local parts stores have zero net cost 'loaner' test tools that you can take advantage of.

shipahoy said:

Can there be something wrong with the TBI system, it's all over 30 years old, I know during idle my injectors have some dripping mixed with spraying when idling, but when I rev it up I get a good solid spray and a smoother running engine?

Click to expand...

The common sense place to start would be to renew the fuel filter if this hasn't been done recently.

I would actually try this first. If replacing the filter doesn't improve the situation, then check the fuel
pressure to see if it is out of specification and follow the data. (Could be as easy as an internal
failed rubber line inside the tank to high resistance electrical connections to the pump's power &
ground point. Worst case, your fuel pump was kind enough to fail in the driveway instead of
on the other side of town.

EDIT: Rereading your 12psi or zero readings. A Standard brand relay should be fine, but given
the total number of potholes/railroad tracks the truck has traversed over the years, how about
pulling the original relay & tighten all the contacts in the relay socket & see if that changes the
behavior. The belt & suspenders repair attempt would be to tighten the female relay sockets
and install a new relay. Your choice.

But we're not going to throw parts at this. (Ready, Fire, Aim mode. :0) Let's change the fuel filter
& see what happens. If no joy, then based upon your need to prime in order to start, then next
step will be to test the fuel pressure and go from there.

EDIT: If you haven't already have them on hand, download the '94 GM Factory Service Manuals
over here: ('88+ GMT400 FSMs)

Happy hunting --