Another AX-15 swap headache

Nuke Proof · Jul 31, 2008

This is my first post on my conversion....
I have an 89 auto with a 242. I got a wrecked 96 with a 5 speed. I put the 96 motor in the 89. I then swapped the intake and exhaust from the 89 motor to the 96 along with all of the other engine mounted sensors.

Then I put an 89 flywheel and a new CPS on the AX-15. The flywheel had all the same notches as the 89 flexplate and I told the auto parts guys the CPS was for a MANUAL and he said okay.

Fooled the NSS (black plug), however the white plug that sits next to the NSS is still disconnected (I thought it was for backup lights and instrument lights for 4 wheel drive?) so I left it disconnected.

My problem is it will turn over but no fire. There is fuel going to the rail, however there is no spark. I know the coil is good because the old motor and trans ran fine. I researched the CPS part number from Napa and saw it is one of two part numbers for that year but neither of them specify which one is for auto or manual.

THE CPS I HAVE HAS TWO WIRES GOING TO THE PLUG. THE OTHER NAPA CPS HAS ONE WIRE TO THE PLUG. WHICH ONE IS THE MANUAL?

I think that when computer is on the cold circuit it is on the closed loop, which to me means the O2 sensor is not used, along with the knock. So those are out, I think.

Any help would be appreciated.

5-90 · Jul 31, 2008

darincraft said:
This is my first post on my conversion....
I have an 89 auto with a 242. I got a wrecked 96 with a 5 speed. I put the 96 motor in the 89. I then swapped the intake and exhaust from the 89 motor to the 96 along with all of the other engine mounted sensors.

Then I put an 89 flywheel and a new CPS on the AX-15. The flywheel had all the same notches as the 89 flexplate and I told the auto parts guys the CPS was for a MANUAL and he said okay.

Fooled the NSS (black plug), however the white plug that sits next to the NSS is still disconnected (I thought it was for backup lights and instrument lights for 4 wheel drive?) so I left it disconnected.

My problem is it will turn over but no fire. There is fuel going to the rail, however there is no spark. I know the coil is good because the old motor and trans ran fine. I researched the CPS part number from Napa and saw it is one of two part numbers for that year but neither of them specify which one is for auto or manual.

THE CPS I HAVE HAS TWO WIRES GOING TO THE PLUG. THE OTHER NAPA CPS HAS ONE WIRE TO THE PLUG. WHICH ONE IS THE MANUAL?

I think that when computer is on the cold circuit it is on the closed loop, which to me means the O2 sensor is not used, along with the knock. So those are out, I think.

Any help would be appreciated.

The CPS has a three-pole connector, but only two are used. There should be two individual wires going into the connector shell (the wires to the CPS are typically bundled as a single wire within about an inch of the connector shell, so that's really not at issue here.)

If there is only one cavity populated on the sensor connector shell, then you have a miswired sensor and need to get another one. "Crank, no start" is commonly caused by a failed CPS (there are some other causes as well, but that's the one we usually run into...)

Stihl029 · Jul 31, 2008

Hmm I am not sure that the CPS info you are speaking of is correct. If I remember correctly the differences are in year, IE Renix vs crysler multipoint injection. I have both an auto (87) and a manual which I have converted to an AX-15 (88). They both use the same sensor, I have swapped them in testing before. I am not sure what the correct P/N is but the new ones I have gotten from Carquest have two wires(one red and one white) in the gm weather pak connector. The manual I have says that the resistance should be 200 Ohms plus of minus 75 Ohms. This should not change much during operation. When you had the Tranny off you should have seen what looked like a second set of teeth on the flywheel, that is what rotates creating the timing signal off a hall effect. Good Luck!!!

Nuke Proof · Jul 31, 2008

When I was at Napa they had two sensor part numbers, one of them only had the red wire going to the weatherpack connector and the other had the red and white. I ended up with the CPS with the two wires.

I know there has been some debate on whether or not the Renix computer ECU system uses a different CPS for manual or auto. Does it, if so I need to try and get the "new" on out and replace it again.

As far as the flywheel goes, I made sure it has the same notches as the flexplate that came out of the 89. It is different than the 96 (the is about three times the notches for the hall effect than the 96).

When you said the resistance is 200 ohms minus 75, is that during operation? Secondly, is this sensor supposed to be magnetic like the 96, if so, I think that is the problem. The new sensor is not magnetized.

Thanks, I really appreciate the help

5-90 · Jul 31, 2008

darincraft said:
When I was at Napa they had two sensor part numbers, one of them only had the red wire going to the weatherpack connector and the other had the red and white. I ended up with the CPS with the two wires.

I know there has been some debate on whether or not the Renix computer ECU system uses a different CPS for manual or auto. Does it, if so I need to try and get the "new" on out and replace it again.

As far as the flywheel goes, I made sure it has the same notches as the flexplate that came out of the 89. It is different than the 96 (the is about three times the notches for the hall effect than the 96).

When you said the resistance is 200 ohms minus 75, is that during operation? Secondly, is this sensor supposed to be magnetic like the 96, if so, I think that is the problem. The new sensor is not magnetized.

Thanks, I really appreciate the help

1) A/T and M/T RENIX CPS units are not RPT not different. I've swapped them before myself (I've had five RENIX rigs, three autos and two manuals.)

2) 200 ohms +/- 75 is with the sensor disconnected, so that is not during operation.

3) Hall Effect sensors tend to be magnetic, but I want to think that the RENIX is not a true "Hall Effect" sensor. I have seen iron filings stick to the thing, but I also know that the later ChryCo sensor will not work with the RENIX, and vice versa. (I've tried this as well. They'll mount the same, and it's easy enough to adapt the wiring, but the damn thing won't start. If one won't work, neither will the other.)

You may want to grab a copy of the RENIX FI manual - I've only ever seen it with 2xpage 58 and 0xpage 59, but it's still useful. I have a .pdf of it on my RENIXPower group - groups.yahoo.com/group/RENIXPower. It's also up at Pirate, and probably other places as well. RENIXPower is a sort of "meeting of the minds" for RENIX systems, you may get replies there that you wouldn't get here. Don't cost nothin' to sign up anyhow. Here's the filename you want - Jeep_Renix_Fuel_Injection_manual.pdf - just make sure you have Acrobat Reader (pretty much any version will do.)

Nuke Proof · Jul 31, 2008

"3) Hall Effect sensors tend to be magnetic, but I want to think that the RENIX is not a true "Hall Effect" sensor. I have seen iron filings stick to the thing, but I also know that the later ChryCo sensor will not work with the RENIX, and vice versa. "

The only reason I asked was the 96 CPS had enough magnetism to pull itself to a wrench about an inch away, but when I laid the "new" CPS on the flywheel there was absolutely no magnatism at all. I knew at that point there was something wrong, but I didn't listen to instinct and instead asked myself, "How can a brand new sensor be bad?" Well the answer is tattooed on the sensor itself, "MADE IN CHINA."

Haven't had a chance to change it, but I'll do that first thing tomorrow

Another AX-15 swap headache

Nuke Proof

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5-90

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Stihl029

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Nuke Proof

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5-90

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Nuke Proof

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