1993 5.7 TBI injectors spray intermittently at start up

[Stu925]

This may be a long one but I’ll give as much info as I can. Truck is a 1993 (build date 6/93 according to door tag) K1500 originally with A/T. Swapped in a good and good running 5.7L and NV 3500 from a 1988 K1500. Engine occasionally won’t start and when that happens injectors are not spraying fuel, fuel pump relay also makes a god awful noise when this happens. Replaced ignition module in distributor as well as fuel pump relay. Problem persists intermittently. Also pulled the ignition switch from above the steering column hoping it was a bad connection or box. Jumping the wires in the plug makes no difference. Tried hooking scanner to it MTG2500 tells me to connect GM1 connector to ALDL port and turn key on then tells me unable to connect so can’t verify any sensors are working. Thinking I may need a different connector for the scanner. When the injectors do spray the pump relay makes no noise and the truck fires right up and idles good some sputtering when you rev it up and it backfires a little bit. Any thoughts on this issue or ALDL connection are appreciated.

 

[Schurkey]

GM1 connector seems right. Unless it's defective, the connector should be correct.

Popped/intermittent ECM fuse or connection?

Possible failed ECM, especially since the ECM controls the fuel pump relay.

 

[Stu925]

GM1 connector seems right. Unless it's defective, the connector should be correct.

Popped/intermittent ECM fuse or connection?

Possible failed ECM, especially since the ECM controls the fuel pump relay.

Fuses all test ok. The further I get into it the more I think the ECM is probably starting to go bad but don’t want to throw a new one at it without confirming it. Is there a way to test the ECM without a scan tool?

 

[Stu925]

Also tried a Snap On Solus scan tool on it with an GM OBD I to OBD II adaptor and it told me it was unable to communicate and voltage to scanner was too low.

 

[Schurkey]

Also tried a Snap On Solus scan tool on it with an GM OBD I to OBD II adaptor and it told me it was unable to communicate and voltage to scanner was too low.

What is the number of that adapter?

I would not expect you need an OBD1 to OBD2 adapter. You'd use the GM1 connector on the end of the regular cable coming out of the Solus.

 

[Stu925]

What is the number of that adapter?

I would not expect you need an OBD1 to OBD2 adapter. You'd use the GM1 connector on the end of the regular cable coming out of the Solus.

Just one I picked up off of Amazon to use my OBD II scanner which didn’t work so borrowed the Solus to try which told me it couldn’t communicate with it because voltage to scanner was too low. Picked the MTG2500 off of Facebook market place specifically for this vehicle and my oldest kids 89 F150. The adapter was billed as GM OBD I to OBD II

 

[fancyTBI]

Just one I picked up off of Amazon to use my OBD II scanner which didn’t work so borrowed the Solus to try which told me it couldn’t communicate with it because voltage to scanner was too low. Picked the MTG2500 off of Facebook market place specifically for this vehicle and my oldest kids 89 F150. The adapter was billed as GM OBD I to OBD II

I can’t help with the injector issue.

However, the OBD1 port on the 88-95 trucks is not powered. My Snap-On Solus Pro will not power on when connected to the OBD1 port. It must either be powered on independently or connected to the 12v/cigarette lighter.

When I had an original battery in the Solus, it wouldn’t power on unless it was connected, if the truck shut off, it would die - not good.

Try connecting the scanner to power, turning it on, then connecting to the OBD1 port, then entering your vehicle data. This might help.

 

[Schurkey]

Snappy has cigarette-lighter, and alligator-clip (battery) power adapters for the OBD1 connectors.

 

[Stu925]

I can’t help with the injector issue.

However, the OBD1 port on the 88-95 trucks is not powered. My Snap-On Solus Pro will not power on when connected to the OBD1 port. It must either be powered on independently or connected to the 12v/cigarette lighter.

When I had an original battery in the Solus, it wouldn’t power on unless it was connected, if the truck shut off, it would die - not good.

Try connecting the scanner to power, turning it on, then connecting to the OBD1 port, then entering your vehicle data. This might help.

I’ll give that a shot. Unit powered up no problem but couldn’t communicate so Maybe I’ll try the GM1 adapter from the MTG2500 with the Solus serial cable. That might work I suppose. If it doesn’t then I suspect the ECM is dying. They’re not super expensive so I may pick one up to see if it solves my issues.

 

[Schurkey]

LOOK at the side of your GM1 connector. There's a port for the power adapter you'll need.