Blinker making the injectors pulse.

[Whit2021]

Hello everyone,

New here and I have searched as much as I could on this topic.

I bought a 1991 c1500 in March of 2020. Drove it home to work and back home and noticed some issues. Cracked head. I have the engine decked and honed, new heads, master rebuild kit etc...mind you this is my first engine to take apart much less build.
I have spark and I have fuel going to the 350 TBI but no pulse at crank. Will start as usual with gas in the tbi, but only a few seconds.

Now, here is where it gets strange. If I have the key in the off position it will make the injectors open and close but sense there is no fuel pressure it just drips out. If I turn the key into the on position the blinker no longer control the injectors and the injectors won’t pulse. I have traced and traced but not finding anything I haven’t taken care of.

Another issue, I have a brown wire from the electronic spark control module that ties into a black and white wire into a ground lug. If I mount it and attach the negative terminal on the battery it starts to melt immediately.

I’ve been going cross eyed for 3 days now trying to figure it out. I am moving tomorrow-Sunday and was hoping to have it running by then. I am aware that is not going to happen. Only other thing I can think to do is buy and entire wiring harness and hope that fixes it.

Any ideas or suggestions would be great. I am all out.

Whit

 

[sewlow]

Check your grounds.
Do 'The Big 3'.
New fuel filter.

 

[618 Syndicate]

First, never, EVER, buy stuff that you "hope" will fix it. It's quite literally throwing money away. If you can't figure it out yourself, you're better off paying someone to diagnose it for you, then at least you know what you need.

This sounds like a ground issue as mentioned above.

 

[Whit2021]

Ok, I’ve reached out to a few shops. Expensive, I’d spend less money starting fresh. I have a harness I can buy for $40.

 

[618 Syndicate]

Ok, I’ve reached out to a few shops. Expensive, I’d spend less money starting fresh. I have a harness I can buy for $40.

If the $40 you spend doesn't fix it, or the $40 after that, or the $40 after that etc, then you're not spending less. All I'm saying is that it's really easy to $40 your budget to death.

 

[Whit2021]

If the $40 you spend doesn't fix it, or the $40 after that, or the $40 after that etc, then you're not spending less. All I'm saying is that it's really easy to $40 your budget to death.

Your definitely on point there. I am already doing the $40 here and $100 there. I reached out to an LS swap guy in a couple of towns over from me.

 

[Schurkey]

I have spark and I have fuel going to the 350 TBI but no pulse at crank. Will start as usual with gas in the tbi, but only a few seconds.

HOW do you know you "have fuel going to the TBI"?

WHAT is the fuel pressure?

Does the pump prime when the key is turned from "Off" to "Run"?

Do you have power to the injectors? They should be powered through fuse(s) any time the key is "on". They should NOT be powered when the key is "Off" or turned to "Accessory". The ECM controls the ground side when it gets a crank signal from the ignition module. If the fuse(s), module, wire harness, or ECM are faulty, the injectors may not fire. (I'm thinking that if the blinker can trigger the injectors, they must be powered and have a ground connection--but maybe not the correct ground.)

If I have the key in the off position it will make the injectors open and close but sense there is no fuel pressure it just drips out. If I turn the key into the on position the blinker no longer control the injectors and the injectors won’t pulse. I have traced and traced but not finding anything I haven’t taken care of.

WHAT is the battery voltage when the blinker operates the injectors? Low battery voltage--or low voltage to various items such as the ECM--can cause no end of screwy operation.

I'm wondering why your injectors have power with the key "Off".

I installed an MSD 5C on a '67 Dodge Dart. If the key was On and the engine not running, the blinker would trigger sparks from the modified electronic ignition system. The blinker created "noise" on the wire harness, and the ignition responded by making sparks. When the engine was running, though, the true ignition signal overcame the "noise" and the engine ran fine.

Another issue, I have a brown wire from the electronic spark control module that ties into a black and white wire into a ground lug. If I mount it and attach the negative terminal on the battery it starts to melt immediately.

Buy or download a service manual including the wiring diagrams. This forum has a selection of .pdf service manuals for free download, yours might be among them. I get most of my service manuals from eBay, used, at advantageous prices. I've also bought some "service manuals on DVD", but I'm not thrilled with that format.

First Guess: the brown wire isn't supposed to be grounded.

 

[Rustjunky67]

DANG Y'ALL!!! Finally we have circumstantial; and possibly imperical, or at least anecdotal evidence for someone who is not low on blinker fluid!!! That's a first I've come across