Renix Engine and fuel control

[NorJeep]

HI,

 

I bought an 86, 2.5 TBI some years back. Havent had much time to play around with it. Just been sitting in my garage.

Recently i decided i wanted to see if i could get it running. I thought its an old quit basic car, how hard could it be... 

My first XJ was a 2.5 TBI same year, and it was very reliable, so i have some renix experience.

 

A bit about the background: 

- Last owner bought it for parts (he rebuilt another truck from 2.5 to a 4l HO) luckily there is not much missing and better he also planed to rebuild this one, so he stocked up with spares (4l spars for the rebuild), but never with the plan of keeping the 2.5.

- Before i bought it it had been sitting for at least 10 years, he thought he drove it to where he stored it, but he was not sure. Last time it had plates was in 98.. so it could have been sitting for close to 30 years.

 

Positive things:

- Engine was turning

- General condition is not bad, don't think it has more than 150k miles (don't now for sure because the dash is missing)

- Electrics seems to be in descent condition.

 

So, down to tech, at this point I'm only interested to see if i can get the engine to fire and run.

- Engine turns by starter when i turn the key.

- ECU has power and are reading signals from most sensors, Including 0,7VAC from CPS messured at the sensor and at the ECU connector, while cranking the engine.

- I pulled out the fule pump and brought it back to life not sure it will produce enough fule pressure or any for that sake, but just to have the components in the control loop.

-By now fule pump runs when i bypass the relay (jumping 30 and 87 on fule pump relay)

One problem is that is dosent prime when ignition is turned to RUN. it has the positive feed from fuse link G on terminal 30, Positiv feed from ignition sw on terminal 86, but i can't seem to get the grounding to activate the relay trough the ECU.

-Same story with the B+ latch relay, this should as far as i know be on all the time the ignition is in run or start and a little while after the engine is shut down. I can trigger the relay by jumping a ground directly to terminal 85, but it won't latch.

Correct me if I'm wrong! there is no conditions where the ECU would not engage the latch relay?

I mean for the fule pump relay there is at least the condition that ECU needs to receive an engine RPM from CPS. Is there any others for the fule pump?

 

After realizing this I'm starting to actually think my ECU could be the problem even if i won't belive it.

Anyone have any in depth knowledge about the ECU? 

 

Grounds between ECU and chassis is good.

 

I havent gotten to much into the ICM, but it dosent give me any sparks. It has power between c213 A and B and on the coil when cranking.

Dose it need the timing input from the ECU on c214 or how dos it work? i think i messured resistance in the coil within spec.

 

Thank you for any input, for a long time i was sure it had to be something simple, and i still hope it is!

 

 

 

 

 

[hgeranium]

38 minutes ago, NorJeep said:

After realizing this I'm starting to actually think my ECU could be the problem even if i won't belive it.

Anyone have any in depth knowledge about the ECU? 

You could try cleaning the connectors of the ECU just to eliminate that possibility. Plus it's a pretty easy fix. Cruiser's writeup is here. Good luck in your hopefully short journey to get it running! Keep us posted.

[Ωhm]

Check ECU Powers & Grounds.

 

C200_1 Ground

C200_2 Ground

C200_3 Ignition

C200_4 Battery

 

 

[eaglescout526]

ICM contacts to the coil are known to corrode and not give a good spark. 

[NorJeep]

I have had the ECU connector off, it looks good and I gave it a quick clean, but I will definitely try another round of cleaning and tighten up the terminals.

 

Grounds on ECU connectors are good.

"Ignition" gets power when ignition is turned to run.

"Battery" has constant power

 

When I measure on ECU connector (with connector connected to ECU) between pin 7 (latch relay) and pin 3 (ignition) I only get about 3vdc with ignition in run. 

This without the relay in the socket.

 

Sensor readings done in the same manner (measured at ECU con, when connected)

- CPS 0.7vac pin 11-28  (170ohm)

- TPS 0.8v - 4.3vdc (while moving sensor) pin 31-13

- MAP 4.5vdc pin 17-33

- air temp 1.8vdc pin 14-32

- coolant temp 1.6vdc 14-32

- O2 0v pin 35-gnd

 

I had the coil of to measure it, terminals seem good.

And I also measured constant power on the coil positive pin (primary side) when it's installed, while cranking.

 

Since timing signal is the only signal the ICM gets from ecu i asume it's also this signals that needs to be present for the ICM to activate the coil? What kind of signal is this? 0-12vdc?

 

Thanks guys, keep it coming!

[NorJeep]

Tried the trick with a 10w light bulb on the injector. Nothing, and no indications of anything on my DMM.

[Ωhm]

During Engine CRANK, look for battery voltage on D1_4. (Start Signal (+))

 

 

 

 

3 hours ago, NorJeep said:

What kind of signal is this? 0-12vdc?

I believe it to be a 5vdc square wave, requiring an oscilloscope (high impedance device) for measuring.

[hgeranium]

@eaglescout526 This is almost starting to look like SoCalManche’s 2.5 lol

[eaglescout526]

1 hour ago, hgeranium said:

@eaglescout526 This is almost starting to look like SoCalManche’s 2.5 lol

Good times. Gooooood times. 

[NorJeep]

can't finned anything on this.. SoCalManche’s 2.5 

link?

 

i vil check D1.4 tomorrow (starter solenoid) Terminal 29 on ECU. is this what tells the ECU that we are in start modus, engine is cranking?

[Eagle_SX4]

19 minutes ago, NorJeep said:

can't finned anything on this.. SoCalManche’s 2.5 

link?

 

i vil check D1.4 tomorrow (starter solenoid) Terminal 29 on ECU. is this what tells the ECU that we are in start modus, engine is cranking?

Pretty sure they are talking about this

 

 

[Ωhm]

41 minutes ago, NorJeep said:

i vil check D1.4 tomorrow (starter solenoid) Terminal 29 on ECU. is this what tells the ECU that we are in start modus, engine is cranking?

 

Yes.

[hgeranium]

1 hour ago, NorJeep said:

can't finned anything on this.. SoCalManche’s 2.5 

link?

Sorry, I didn’t mean to throw you off. I mentioned it because eaglescout and Ωhm helped SoCalManche a few years ago with a no start that ended up taking 25 pages of thread for him to figure it out. Hopefully yours doesn’t go for that long lol. IIRC (one of) his problem was something about a bad injector that tested good but didn’t actually work.

[eaglescout526]

8 minutes ago, hgeranium said:

IIRC (one of) his problem was something about a bad injector that tested good but didn’t actually work.

Correct