88 crank no start

[B.RAIDER]

I asked this question back in post #13

Do you have 12 volts to the ignition wire at the 3 prong plug and do you have a tach signal from the other plug?

When you have the no spark situation (verified with checker) is there 12 volts there?

 

[joe_peters]

Intermittent spark.

Coil. Coil to ICM clips. ICM. B Latch relay. ECU. Crank sensor. Harness between any of the aforementioned.

Note: there are numerous grounds to the DIPSTICK tube--ICM, ECU, o2 sensor and others. Make sure to strip things down to bare metal, treat with an anti-corrosive agent, and make the connections TIGHT.

Note: there is a POS braided strap from the rear of the head to the firewall. It is the one and only XJ unibody ground on the early rigs. Replace the strap with a 4 or 2 ga cable, strip down to bare metal, treat with an anti-corrosive, and make the connection TIGHT.

Good luck.

 

[buzzbombxj]

remove the fuel pump, I had a very similar problem and it ended up being the fuel line between the pump and the sender, it was not holding the pressure......

I know for certain that I am not getting spark most of the time. When I would crank it over to try to start it the tailpipe smelled like gas, and whenever I poke the Schrader valve in my fuel rail gas squirts like old faithful. I don't think that is the problem, when I can get spark every time I will move on to fuel systems.

I asked this question back in post #13

Do you have 12 volts to the ignition wire at the 3 prong plug and do you have a tach signal from the other plug?

When you have the no spark situation (verified with checker) is there 12 volts there?

Today when I tried to check I did not have enough battery voltage to crank over, but I was able to get the same voltage at the 3-prong connector. The battery is on charge now so I can really test it. I think all this charging and discharging has finally taken a toll on my battery. Can I measure my tach signal with a multi meter?

Intermittent spark.
Coil. Coil to ICM clips. ICM. B Latch relay. ECU. Crank sensor. Harness between any of the aforementioned.

Note: there are numerous grounds to the DIPSTICK tube--ICM, ECU, o2 sensor and others. Make sure to strip things down to bare metal, treat with an anti-corrosive agent, and make the connections TIGHT.

Note: there is a POS braided strap from the rear of the head to the firewall. It is the one and only XJ unibody ground on the early rigs. Replace the strap with a 4 or 2 ga cable, strip down to bare metal, treat with an anti-corrosive, and make the connection TIGHT.

Good luck.

Coil is new, coil to icm clip things were cleaned with electric contact cleaner, and then smeared with dielectric grease. Icm is new; connectors were cleaned with electric contact cleaner, then smeared with dielectric grease. Ecu is new. crank sensor is new. I checked the harness for continuity it said it was fine but nowadays I’m second-guessing everything. I took apart every connector I found (that wasn’t obviously to the lights or anything) and sprayed it liberally with electric contact cleaner, then smeared with dielectric grease

What is a B latch relay? I don’t think I have replaced that.

Dipstick grounds were moved one threaded hole over because that hole was stripped out, but it was wire brushed, cleaned with electric contact cleaner, then smeared with dielectric grease.

I added one more battery ground to the fender.

I left the pos braided strap in place, but supplemented it with another ground, cleaned with electric contact cleaner, then smeared with dielectric grease. Both of my new grounds have thicker wire than my battery cables haha.

There is a common problem with the C101 connector above the brake booster. Jeep recommended cutting it out and wiring direct.

I found this advice from the first page I forgot to implement! I will give this a go too, I forgot about it. :dunce:

Thanks again for this great help!

 

[joe_peters]

You have three or four black relays in a row on the passenger side fenderwell.

If no a/c, you will have only three.

Those relays are B Latch relay--provides 12 volts to the primary windings of the coil, provides 12 volts direct to the fuel pump for the 3-second prime; the fuel pump relay; the oxygen heater relay; and if so equipped the a/c clutch relay.

Link to diagram: http://allinfoaboutautorepairs.com/uploads/images/chrysler/42276757-b.gif

Note that some XJs have been found to have the relays assigned in different positions, a little testing never hurts.

 

[buzzbombxj]

My battery doesn’t hold a charge anymore, so I’m kind of paused until I can get a new one.

http://www.optimabatteries.com/optima_products/yellowtop/specs.php

I am looking for a d75/25, (looks to be the closest in dimensions) but nobody seems to have one. I might have to get a 34/78, cause that’s the only one I can find around my area, but I would have to modify my battery tray to get it to fit and it would be 13/16ths taller than my current battery instead of 5/8s. I’m trying to buy one today.

 

[buzzbombxj]

My whole life it seems I have wanted an optima, now I am the proud new owner of a 34/78 yellow. I eventually found a place that had yellow tops in stock, only one Costco had them, half hour away, and this was the only size. Picked it up and threw it in with some new goodies with kragen. My jeep was so impressed by a 750 cca slap to the face that it started, twice. I have battery voltage at the 3-prong connector that goes into the ICM. I am super excited to work on my jeep tomorrow!

 

[eduyan]

Have the same starting issues. Cranks but wont start. Replaced, coil, distributor cap, spark plug wires and Oxygen sensor. A year ago, the camshaft positioning was also replaced and the neutral safety switch was cleaned and re-installed.

It only cranks when in Park but not in neutral. Could this be the problem? If I need to replace more parts, I want to start from the least expensive. Camshaft Positioning Sensor ($70 from NAPA), Neutral Switch Safety Switch ($140 from Quadratec) and electronic control module (approximately $300).

Or what else could have gone bad? I prefer not to spend anymore. Help!!!!

 

[eduyan]

by the way..

1996 Jeep Cherokee 4L Automatic with 195K miles, was running very good until it wont start anymore.

 

[joe_peters]

Have the same starting issues. Cranks but wont start. Replaced, coil, distributor cap, spark plug wires and Oxygen sensor. A year ago, the camshaft positioning was also replaced and the neutral safety switch was cleaned and re-installed.

It only cranks when in Park but not in neutral. Could this be the problem? If I need to replace more parts, I want to start from the least expensive. Camshaft Positioning Sensor ($70 from NAPA), Neutral Switch Safety Switch ($140 from Quadratec) and electronic control module (approximately $300).

Or what else could have gone bad? I prefer not to spend anymore. Help!!!!

If it cranks the NSS is not your problem. The NSS may not be adjusted properly preventing cranking in neutral. The NSS simply interrupts the starter relay ground unless the gear selector is in PARK or NEUTRAL.

Ok, cranks, but won't fire. What is the missing element? Spark, fuel, compression? Use a spare plug or pull one plug from the engine. Seat the spark plug wire on the plug. Ground the metal plug body to the engine. Crank the engine--got a snappy blue spark? No spark, solve for that. Not a snappy blue spark, solve for that. If you have a snappy blue spark move on to fuel and compression.

Fuel--do you have fuel pressure at the rail? Is the pressure to spec? If no pressure, solve for that. If pressure but not up to spec, solve for that. If you have pressure, and the pressure is within spec, then you need to determine if the injectors are receiving 12 volts with a meter, if not solve for that. If the injectors are getting voltage, you need to determine if they are getting a firing impulse from the PCM with a high-end meter or a NOID light ($3). No firing impulse, solve for that.

If you have spark, fuel, injectors working, and it still won't fire off post back up.

 

[eduyan]

Traveling for work today. I will try to work on it this weekend. Thanks for the quick reply.

 

[eduyan]

Totally stumped, I didn't want to spend more money replacing parts that might be perfectly fine. Had AAA tow the Cherokee to my neighborhood gas station garage. My mechanic spend a couple of hours finding out what wire has gone wrong. He told me it is the ground from the engine to the firewall, it was badly corroded. cost me $125 and i am happy. I was getting ready to replace the PCM. I gave the Xj to my 17 year old son for his birthday. He is very happy that it is running again.

Thanks for all your suggestions and comments.

 

[joe_peters]

That POS braided strap ground was discussed twice in this thread, they have been the source of many a problem. Hope your mechanic replaced it with a good 4 or 2 gauge cable.

Good luck.

 

[buzzbombxj]

Update to my fail thread: I spliced that connector together, built a battery tray and installed my optima. All well and good but the problem is still the same. I essentially gave up and started saving up money to take it to a shop, where they will smog it also. First time in about 4 years. This thread is proof that advice is only as good as the bonehead trying to apply it!

When I get it back from the shop I will post up what the tech said the issue was, no matter how simple or embarrassing it is I will just be happy to have my jeep back.

Thank you again for all the help!

 

[buzzbombxj]

Crankshaft position sensor :confused1

That was it. My brand new cps, that I thought was the problem, but no, it’s brand new, that can’t be it. On the plus side I have my jeep back, it runs like a top, and I will be able to drive it around pretty soon!