I am currently swaping an 89 TBI 350 into my Jeep. Right now I have everything wired up correctly (I think) but the engine will not start up without dumping a little bit of fuel down the throttle body first. After that it will run fine. I have spent the past 5 hours searching through old TBI posts to try and find the solution to my problem but with no luck. Any ideas would be great. I am out of them!!!!

Sounds like you may not have the "cranking signal" wire to the ECM hooked up.

ignition feed to the computor also needs voltage while cranking. Common mistake

ignition feed to the computor also needs voltage while cranking. Common mistake

Crap!!! Why didn't I catch that??? Im done with the heep tonight I'll try that tomorrow after work and report back what happens. Thanks a lot!!!

Sounds like you may not have the "cranking signal" wire to the ECM hooked up.

I didn't at first,I jumped straight to the battery hoping that would be the problem, it wasn't. Thanks for the input though!

AFAIK the C9 crank signal wire has nothing to do with turning on the injector during cranking.
As i know it, it only tells the ECM it's cranking and then based on the temp it will increase the amount of fuel being squirted.

Now thinking about what he said...
the engine will not start up without dumping a little bit of fuel down the throttle body first

Tells me he has spark all the time while cranking, this means he has voltage to the coil at least, while cranking. Now if he did not follow any of the GM diagrams and just started twisting wires together to see if it fires up...then we really don't know where/when his ECM is getting power.

But if he had actually read any of the other threads about TBI even within the last 2 days.....there is another TBI thread that describes what is needed to have spark and fuel.

The ECM will not fire the injectors until it recieves the signal from the distr telling it there is spark.

It can't squirt fuel if there is no fuel pressure.
So what is the pressure.
The sheet 1 of the wiring diagrams have voltage checks listed on them..did you do them yet?

Do you have 12V setting on the red and white wires going to the injectors with the key on and when cranking?


Give some more details on the install...what wiring diagram did you follow?

It can't squirt fuel if there is no fuel pressure.
So what is the pressure.
The sheet 1 of the wiring diagrams have voltage checks listed on them..did you do them yet?

Do you have 12V setting on the red and white wires going to the injectors with the key on and when cranking?


Give some more details on the install...what wiring diagram did you follow?

I have good fuel pressure at 13 psi or so. Did all my voltage checks, checked out good. Don't know about having 12v on the injector wires when cranking yet, if not where should I look for the problem? Thanks for the help

Couple of questiones: Can you see fuel squirting from the injectors while the motor is cranking? If yes, is the ECT properly connected? When engine temps are low, the ECT tells the engine to enrichen the mixture. If you can see gas being injected while cranking, and the addition of a little more, via pouring it down the throttle body, would imply an ECT problem. Last questione: any codes being set?

Read down a few more threads, and came accross this one that appers on point four problem: http://www.pirate4x4.com/forum/showthread.php?t=593182

Couple of questiones: Can you see fuel squirting from the injectors while the motor is cranking? If yes, is the ECT properly connected? When engine temps are low, the ECT tells the engine to enrichen the mixture. If you can see gas being injected while cranking, and the addition of a little more, via pouring it down the throttle body, would imply an ECT problem. Last questione: any codes being set?

No, I see no fuel squirting from the injectors, but if I dump fuel into the throttle body and get the engine to run, plenty of fuel comes out. I have not been clear on something, the engine will not fire until I let off the ignition switch. I have to crank on the engine for 3 to 5 sec then stop cranking and she fires up. Could I have something hooked up wrong? Im pretty sure that I have checked all wires but I may have missed somethin. Thanks again

No, I see no fuel squirting from the injectors, but if I dump fuel into the throttle body and get the engine to run, plenty of fuel comes out. I have not been clear on something, the engine will not fire until I let off the ignition switch. I have to crank on the engine for 3 to 5 sec then stop cranking and she fires up. Could I have something hooked up wrong? Im pretty sure that I have checked all wires but I may have missed somethin. Thanks again

You have something hooked up to a power source that gets power when the key is on, but does not get power when the key is in the cranking position. That's why is won't start when your cranking, but as soon as you let go of the key and it returns to the on position, the circuit gets power and the engine is still turning over... hits and starts.

I'm guessing it's probably your ignition circuit that's not getting power in the cranking mode like Bill alluded to his post.

You should not be running your system off any of the trucks wiring!!!

Your power on the pink/blk wires should be 12V when "key on" and start. This power should be connected to a relay that is energized by the wire that used to go to the + side of the coil. That is normally the only one that is hot in both positions.
You can also run the 12V to the injectors from the output of the same relay.

Do not run power straight to the ECM or the injectors or even the coil, straight from the truck wiring.
You should run the fuel pump on it's own relay.
Check the wiring thread at the FI forum in my sig.
You need to follow the wiring diagram and connect it all properly.
Then see how it does.

You should not be running your system off any of the trucks wiring!!!

Your power on the pink/blk wires should be 12V when "key on" and start. This power should be connected to a relay that is energized by the wire that used to go to the + side of the coil. That is normally the only one that is hot in both positions.
You can also run the 12V to the injectors from the output of the same relay.

Do not run power straight to the ECM or the injectors or even the coil, straight from the truck wiring.
You should run the fuel pump on it's own relay.
Check the wiring thread at the FI forum in my sig.
You need to follow the wiring diagram and connect it all properly.
Then see how it does.

Why not use the Jeep wire harness to make this system work? Can you explain this to me? I figured this would be the best way to go. Fuel pump is already on its own relay.

1. voltage drop
2. old wiring
3. makes for inconsistent operation

When you transplant a motor with the modified factory harness or just buy a ready made harness, there are only a few wires that need to be tied in to the vehicle.

12V from the main starter post or the B+ term of the alter.
This goes to the power for the relays and to the bat(org) wire in the harness.

ground to the block tied to the blk/wht wire in the harness

switched 12V to energize the relays from the ign switch

etc...as in the "what wires do I need thread" in the link in my sig.