TBI Help!

jeepmedic

jeepmedic

Good enough for Gov't work!
Joined
Feb 2, 2013
Location
Cameron N.C.
I have a 1987 Wrangler with a 1987 SB TBI 350/700r4/np 231 out of a R10 pickup installed in it. I bought the jeep as a unfinished project from a guy who did some things half assed but it ran, sorta lol. My problem is the jeep honestly runs like shit. I have a suburban that I have been swapping working parts off of and havent found any sensors that are bad. The wiring haness is a splice job by the previous owner so its questionable at best and the ECM is a new 1227747.

MY questions are:

-Should I buy a new Howell harness and skip the cut and hackjob wiring?

-My fuel pump runs constatnly with switch on and the motor not running, is this normal because on the suburban it does not it builds pressure then shuts off

-If I goto a new harness should I install a manual pickup with an inline pump?

Thanks for any replies. I am at my wits end with this POS.
 
Howell sells repair guide for TBI for about $12. The fuel pump should come when key is first turned on then will cut off if motor doesn't run. It doesn't matter where the pump is as long as you have at least 12 lbs and an open return line to tank from the throttle body. You may need to change or re program the prom in the ECM Howell can take of this. Howell's harness is great, they got everything figured out and instructions are good.
 
Do you have a check engine light, is it on? Can you check for codes from ecm?
 
No check engine light. I checked for codes but got nothing. I replaced the fuel pump and still ran like crap. Crazy thing is I unplugged tthe coolant temp sensor and it ran alot better....:confused: Any ideas?
 
jeepmedic said:
No check engine light. I checked for codes but got nothing. I replaced the fuel pump and still ran like crap. Crazy thing is I unplugged tthe coolant temp sensor and it ran alot better....:confused: Any ideas?
Click to expand...
Maybe you have a bad coolant temp sensor? Call Howell, they can troubleshoot over the phone.
 
Referring to descriptions from the original post:
1. it was an unfinished project
2. the work was half-assed
3. it runs like shit
4. you are swapping parts from another vehicle that may, or may not be a correct match
5. the wiring harness is a splice job by a previous owner so it's questionable at best

The first thing I would do is pull all the connectors off all the sensors and also the two connectors out of the ECM. Then, get an OHM meter and a long enough piece of good wire to allow you to check each individual wire in the harness for continuity. Once that is done (assuming all check OK), I would carefully check all the grounds. Be aware of the 5v reference that is common between the MAP sensor and TPS. There is also a sensor ground that is common between the TPS and CTS. With the low voltages all wiring and connectors have to be right, including grounds.

If you come across any splices that look like crap the chances will be good that the rest of them will be the same. That would be the time to make the decision to fix or replace the harness.
 
I was swapping out a 4.3 last year and the plastic top on coolant temp sensor broke off. I could still connect wires and run engine. I bought new sensor and engine ran terrible. Tried another brand and solved problem. They can be checked at temperature with an ohm meter.
 
moldman05 said:
I was swapping out a 4.3 last year and the plastic top on coolant temp sensor broke off. I could still connect wires and run engine. I bought new sensor and engine ran terrible. Tried another brand and solved problem. They can be checked at temperature with an ohm meter.
Click to expand...

Do you by chance know the ohm specs?
 
One thing that hung me up on my TBI swap a couple years ago was trying to run my fuel pump ground too far away from the actual pump. Drove me NUTS, it ran like crap, would act like it was over heating, not run at all, etc. Once I moved the ground on the pump to within a foot of the pump, it ran like a top for the next 3 years.
 
bbaxter51 said:
One thing that hung me up on my TBI swap a couple years ago was trying to run my fuel pump ground too far away from the actual pump. Drove me NUTS, it ran like crap, would act like it was over heating, not run at all, etc. Once I moved the ground on the pump to within a foot of the pump, it ran like a top for the next 3 years.
Click to expand...
I had this same issue and the new ground fixed mine also.
 
jeepmedic said:
-My fuel pump runs constatnly with switch on and the motor not running, is this normal because on the suburban it does not it builds pressure then shuts off
Click to expand...

This was the first thing I did when mine was driving me crazy, I bypassed the computer and wired the pump to the key on power switch. It's possible the PO did the same thing.
 
bbaxter51 said:
This was the first thing I did when mine was driving me crazy, I bypassed the computer and wired the pump to the key on power switch. It's possible the PO did the same thing.
Click to expand...

Im pretty sure its hard wired. Im almost ready to give Affordable FI a call and drop $400 bucks to end the shenanigans... First Im going to put in the old Coolant temp sender and see if that works, I replaced the pump and sender this weekend.
 
I have what you need. PM if interested.
BNIB afi tbi harness.
And some wisdom.
 
According to Howell the ohms for coolant temperature sensor is 100,000 ohms @ -40F and 70 ohms @ 266F. I checked mine at operating temp and it was about 400 ohms and another at ambient was about 2000 ohms.
 
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