chevy tbi conversion problems

[harkinoff]

bought this cj5, someone did a tbi conversion on it. The idle has been crazy on it. Hi then low, surging thing at idle. Going down the road it seems fine. Last nite going home it just dies. pull over cycle key and it fires like nothing had happened. Go out this morning for work, cranks but doesn't even try to fire. has spark. i don't hear the fuel pump though. Checked fuses and connections, everything looks great.

What are things to look for. It does have a plug on dash to troubleshoot. Who works on these things. I miss my propane!

 

[Tacoma]

Is it the stock diagnostic plug? If it is, you can use a paper clip to get the codes.

You could have a whole host of issues with the symptoms you're describing. Vacuum leaks, bad sensors (luckily there aren't many, and mostly they either work or they don't), etc etc.

Get some codes and report back. I have factory manuals that may help.

 

[soda blaster]

try closing off the egr valve.

 

[harkinoff]

I'm guessing stock plug. Could pull it down to autozone and get the codes brought up? The kit has a red led on the dash. Cycling the key doesn't bring any codes up. guessing the chevy computer needs a computer to read codes. tonite after work, going to check and see if fuel pump has power to it or if it is siezed, might be that simple?

 

[UNSTUCK]

It might be that simple. The ECU controls the fuel pump relay. So if the relay is switching, you need to follow power down streem. If the relay is not switching, find out if your signal wire is hot while cranking. It should be hot for 2 seconds when you first turn the key on, but then truns off. You can check it then, but also check while cranking. That will let you know if you have a ECU problem, a relay problem, wire problems, or a pump problem. If the fuel tank has been run out lately, that can burn the pump up. Also if that LED you have doesn't turn on with the key on that can indicate an ECU problem. Like Tacoma said use a jumper wire on the aldl to check codes, with the key one. If i remember right, pin 9 is the data streem and pin 16 power for the other end, but double check that first. That will save you from dragging the thing to auto zone or where ever.

 

[mbryson]

Randy, just "hot wire" the pump to see if it works. If it does, try to fire the motor.

 

[Crinco]

You said this is a kit? Is it new? The LED on the dash should have turned on when you were driving home, but either way as long as you don't unplug the battery then the code should still be there. Do a Google search to learn how to pull the codes and get a list of the codes and possible solutions.
This is a GM style kit and not a Holley kit right? Pull those codes and let us know what the ECM is telling you.

 

[harkinoff]

didn't have any luck pulling codes. I did meter out each part, took apart computer etc. went through all wiring. directly wired fuel pump and it runs great. Started tracing wires to computer and out to sensors. came to this. It runs sometimes on its own plugged in, always runs and starts unplugged. don't know what it is, but is the problem. Not bad troubleshooting without a book or manual. figured after work head to parts store. atleast i have an idea how and what makes this pile run. just figure out whats what and names now. all i know about this system is that it looks all stock chevy. I couldn't see any mods in the computer, jumper etc no fresh solder marks.

 

[I Lean]

That looks like a MAP sensor.

 

[Tacoma]

That IS a MAP sensor.

What usually screws up on GM TBI is the EGR system, but I've had MAP sensors go out too.

 

[jsudar]

Get a volt meter on that and apply vacuum to the port and see if the resistance changes. A map sensor has a lot to do with how much fuel the engine gets, but I don't think I've ever seen one make an engine die and not restart.

If it has a stock GM fuel pump, check that first 'cause they suck (no pun intended). If it has an aftermarket frame rail mounted pump check that too. I have seen a lot of those die since when the get starved for fuel or they just get too hot since they aren't in the tank with the fuel to cool them.

 

[harkinoff]

It has a frame mounted fuel pump. It has been running better, still have to jumper out fuel pump to get it started sometimes. Idle often gets all out of control. Thought about just hitting wrecking yard and getting all sensors and throwing them one by one? I haven't had any luck on getting codes yet. I've just been driving it to work everyday. No other problems besides it leaks oil like a bastard... Anybody know who built this thing, its from up north I guess? It would be nice to know some history on it...

 

[Tacoma]

If you're gonna get all berserk about this and start pulling out your hair, I could probably get the factory test procedures for all the sensors scanned... or you could PM me and I'll type them up.

 

[harkinoff]

Not going crazy yet.... Just putting it off I've put about 2500 miles on it this way he he he. Everytime The engine light comes on, I'm heading for work or something besides going and getting codes.

Pulling the codes would be way cool of you! Thanks

I did check voltage off of the relay for the fuel pump, I do get voltage for a couple of seconds. The start circuit seems to be working. I wonder if their is a pressure switch, if it sees fuel pressure etc. Or is it just the oil pressure? When I jumper thefuel pump directly off of the battery, you can hear gurgling noises at the tbi. It always starts that way though.

 

[Tacoma]

The codes don't reset for awhile, like 50 starts or when you pull the battery cables. So check 'em.

I will try and get the relevant test pages scanned tomorrow. And what all the codes are.