1986 TBI 2.5 no start/crank

[90xj06]

ahh i see. i don't know much about the early 2.5 but if they didn't put in some kind of fail safe its going to see that sensor as really hot or really cold. and will effect mixtures. normally they give it a best guess time map to compensate. but again i'm not sure.


Edit. had a buddy check his 2.5 tbi and it starts without the CTS

 

[Ecomike]

ahh i see. i don't know much about the early 2.5 but if they didn't put in some kind of fail safe its going to see that sensor as really hot or really cold. and will effect mixtures. normally they give it a best guess time map to compensate. but again i'm not sure.


Edit. had a buddy check his 2.5 tbi and it starts without the CTS

Interesting. My 87 had temperature sensitive no starts when the MAT/IAT sensor went bad. It would not start on cold mornings.

If he has more than one issue, the combination of bad CTS might be the issue, but IIRC Old_man had a gas guzzler episode that turned out to be dead CTS reading -40F all the time and it started, but what if it read 250 Or did not read at all. I always wonder how critical the CTS might be to starting.

I have always read the CPS signal, spark, fuel, cranking speed and cranking battery voltage were the main issues for Renix to start. But too much or too little air or fuel, mainly too much fuel or too little air, that cause flooding are the typical issue when the plugs are wet on inspection and one has spark and proper timing

Stardust, you are sure that you have spark right? Is it a hot spark?

 

[Ecomike]

Sounds like it is time to get the 86 Renix 2.5 throttle body injection manual and see it what it says and what the sensor readings should be in the run position on the ign switch. 5-90 had a Yahoo board for ages that had the old pdfs but I think the pdfs may be gone, or you need to be a member and I am not sure 5-90 is manning that board these days.

You might ask cruiser54 if he has one???? He is the real expert, worked at a dealership back in the renix days...saw it all.

 

[stardust2280]

I will check again, but yes I am sure that I had spark. That's unfortunate that it does start without the CTS... I guess I will replace it since its already shipped. How could I get ahold of Cruiser?

 

[Ecomike]

I will check again, but yes I am sure that I had spark. That's unfortunate that it does start without the CTS... I guess I will replace it since its already shipped. How could I get ahold of Cruiser?

I sent him a message. Do you have PM ability here?

 

[Jeep Driver]

Yes, it should run without the coolant sensor.

 

[stardust2280]

I sent him a message. Do you have PM ability here?

Yes, I do. Thanks. Where would I get such a manual?

 

[Ecomike]

Yes, I do. Thanks. Where would I get such a manual?

Anywhere you can still find one and pry it out of the owners hands LOL.

Here are some clues

https://www.google.com/search?q=1986+jeep+2.5+service+manaul&ie=utf-8&oe=utf-8

Back about 15 years ago I found and accessed mine at the local public library in the reference section. No idea if they still keep those, may depend on the Library.

 

[cruiser54]

I will check again, but yes I am sure that I had spark. That's unfortunate that it does start without the CTS... I guess I will replace it since its already shipped. How could I get ahold of Cruiser?

Mike got ahold of me. Slow down on parts replacement.

I am way more familiar with the 4.0 than the 2.5, but let's give this a shot.
Have you checked fuel pressure?

Verified a bright blue spark?

I'd like you to visit my site. www.cruiser54.com and do Tips 1,2,3 and 4. Just cuz.

 

[stardust2280]

Cruiser, thanks for chiming in.

Fuel pressure will be checked today, life got ahead of me the past few days.
I will verify again today, but last time I checked spark was bright and blue.

I will do those tips too, but I dont think my jeep has the C101 connection... I have seen your tips before and looked into the C101 connection but as far as I can tell there isn't one under the hood.

 

[cruiser54]

http://i1354.photobucket.com/albums...ch Photos/C101 connector open_zps0t9xxa1k.jpg

 

[cruiser54]

 

[stardust2280]

Yeah, just checked, that isn't in my jeep. Either it was removed before or it was made without one.

 

[stardust2280]

Do I check the fuel pressure by just priming the fuel pump and leaving the ignition in the ON position? Since it won't start.

 

[Ecomike]

Do I check the fuel pressure by just priming the fuel pump and leaving the ignition in the ON position? Since it won't start.

I would assume so, yes. Check your email. You may have a closed throttle switch as well as the WOT switch and the idle stepper motor?

Your rig is probably too early but the 87-90 had a bizarre power to fuel pump wiring set up that had three routs to power the fuel pump, one was timed during the first switch to run position, the second was route for cranking, the third a rout for running. 8MUD is the expert here on that nightmare. So you may need to check fuel pressure before and during cranking!!!!!

 

[stardust2280]

I would assume so, yes. Check your email. You may have a closed throttle switch as well as the WOT switch and the idle stepper motor?

Your rig is probably too early but the 87-90 had a bizarre power to fuel pump wiring set up that had three routs to power the fuel pump, one was timed during the first switch to run position, the second was route for cranking, the third a rout for running. 8MUD is the expert here on that nightmare. So you may need to check fuel pressure before and during cranking!!!!!

I will check it during and before cranking then. I checked my email but didn't get anything, I sent you an email though just in case I wrote mine wrong.

 

[Ecomike]

I will check it during and before cranking then. I checked my email but didn't get anything, I sent you an email though just in case I wrote mine wrong.

I sent the email to the stsn...email? In reply to you?

 

[Ecomike]

I will check it during and before cranking then. I checked my email but didn't get anything, I sent you an email though just in case I wrote mine wrong.

Check again now, and check your spam folder?

 

[stardust2280]

Got it, thanks.

 

[stardust2280]

Cyl 1: 0
Cyl 2: 80
Cyl 3: 0
Cyl 4: 85
Those are #'s from the compression test I did today.
I only had enough oil from the bottom of a can to do one wet test, which I did on cyl 1, results were still 0.

Spark plugs, just from cranking and brand new:
Cyl 1: good
Cyl 2: fowled (blackened)
Cyl 3: good
Cyl 4: Fowled badly
Hindsight is 20/20, should have used the gauge at the beginning. Anyway, nothing I can do about that now.
I don't know if its a head gasket because alternate cylinders have no compression.
I think if a head gasket blew it would be cylinders next to one another, but this is cyl 2 and 4, so it seems unlikely to me that the head gasket went out in both places at the same time? Any thoughts?