TBI Problem

Granny

Granny

One day at a time...
Joined
Jun 12, 2007
Location
Cabarrus County (Rimertown)
Some good news... and also a slight problem to go along with it!

I finally got the TBI installed in my little CJ-5. The difference is positively unbelievable. I have owned this Jeep for 29 years and it has never ran like this. It runs like a scalded dog!

On the down side, it has also developed a problem. The first few start-ups and shut-downs went fine. Then all of a sudden it cranks but won't start again. I went over my work and found nothing out of order so I finally dumped a small amount of gas in it and it started right up. I had to do this several times today to get it to start. Once running, all is well. I Googled a suggestion that possibly the pickup coil in the distributor has gone bad, and that can cause this. I'll probably pick up on it again on Monday.

Any of you guys got an suggestions... I'm all ears. :)
 
Odd! I assume the fuelpump runs for a couple seconds when key-on?

Does it not start both cold or hot?
Was your tank clean before hand?
Could be a suction loss (clogged sock or PRE-fuelpump filter)?

Have you run logger on it during cranking? Might show an issue with all the sensors IAC, TPS, CTS, etc.
 
↑ ↑ ↑ ↑ ↑

Fuel pump is working fine... 13 psi constant, steady pressure.

Same issue, hot or cold.
Tank is clean, all new (for ethanol) hoses.
There is no sock, new filter, perfectly clear.

Have not run data logger yet. All in good time. :)
 
Actually I have run into that on a few gm tbi motors and it was the pickup.
I guess the signal to fire the injectors is weak at cranking rpm idk.
Don do you have a noid light to plug in the injector harness to verify that this is the issue.
Also are we working with new or used parts?

Sent from my GT-P3113 using Tapatalk 2
 
I appreciate the reply, Chris. I don't have a noid light. I am working with used parts, but I do have two of every sensor, including a distributor pickup.

I believe I may have found a possible error in my wiring. Not certain yet, but will look more into it tomorrow. I will post results.
 
I spent all day improving and verifying ground connections. I retraced all my connections. I borrowed a noid light from a good friend. All this and still no start. I finally found a good TBI troubleshooting guide, compliments of Google, and started down the ladder. Finally, it jumped out an smacked me... a damned faulty in-line fuse holder. I jumped it out and all is well. I put a total of 3 in-line fuses in the wiring as recommended. Tomorrow, I go to town and buy 3 brand new ones (good ones) and replace all of them. It has been an adventure, but my wiring was OK as was. :shaking:
 
Just FYI in the future a regular 12v test light will work as a noid light. I've also used a little 194 bulb and socket pigtail like a side marker light before.

Sent from my XT907 using Tapatalk 2
 
Hey Tim. That's good to know, appreciate the info.

I completed the wiring today. We now have three "GOOD" in-line fuse holders. I put all new loom on the wiring, and have the engine compartment cleaned up pretty nice. Tomorrow I plan to follow Bill Hamilton's setup sheet and make some adjustments, if needed. After that, I believe I will hook up the laptop, start WinALDL, and take the wife and grandkids on a nice couple-hour drive to log some data for my programming Guru.

Caver Dave... be watching your email! :)
 
Injectors. Don't ask for an explanation... nothing makes sense at all, but cutting the inline fuse holder out and replacing it with a jumper make the problem go away. We now have three "NEW" "GOOD QUALITY" fuse holder in place, and all is well again. :bounce: :bounce2:
 
Well, I put my foot in my mouth again and doesn't taste too good. :shaking: I said all was well with this TBI project, but all is NOT well.

The Jeep still runs real good after it gets warmed up; in fact, it still runs like a scalded dog, BUT it is running way too lean. When cold-started after sitting over night the idle is erratic and cycles up and down. It will finally settle down after warming up a bit. Upon the advice of a local mechanic, I played with the TPS voltage taking it up to .65v and upping the fuel pressure. It really made no difference. I have also put in "NEW" IAC, TPS and O2 sensors with no noticable difference. Finally, today I put the TPS back to .54v and reset the IAC. Then, I pulled the custom chip out of the ECM and put the factory Chevy chip back in. It doesn't run as well, but the IAC counts settled down and the O2 sensor is reading within an acceptable range. So I am at a point where I have to decide what to do next. I still don't know how to decipher the log data and that too leaves me in a bad situation. I have been plugging away at this thing far too long, and I welcome any advice.
 
I just saw this. Did you get it figured out? I can give you some things to run by your tuner once I get home. I fought some surging idle on my truck til I got it dialed in.

Sent from my XT907 using Tapatalk 2
 
Hi Tim... YES and NO... the custom chip I tried ended up being the wrong tune. That was the sole cause of all the problems. It was way too lean, and caused all sorts of start-up and idling problems. After warm-up it ran like a scalded dog, but again way too lean. A local mechanic, who is said to be pretty sharp on this sort of stuff, told me I was flirting with burning a piston.

Anyway, right now I am running the stock Chevy 5.0L chip that came in the ECM. I have the timing set back 10° and the Jeep seems mostly content with it. It is a wee bit sluggish below 1500-1600 rpm, and will bog if punched hard off idle, but otherwise it runs real decent. It pulled my boat yesterday with no problem at all. I still get an SES because of no VSS sensor, but that is just a minor annoyance. I am waiting to see what happens for another week or two. After that I will explore some other options.

Appreciate you asking. :)
 
Brother Don... been out of town for weeks. I'll see if I can cipher the GM5.0 BPW & Fuel tables to adjust the fuel in the existing tune, since the timing is so close.
 
Back
Top