No Start, Please Help

'91 XJ, 4L, AW4

I drove the Jeep into the garage yesterday with no problems. Today I went to start it and got a terrible grinding noise. I had been rolling it across the garage floor and think I left the transfercase between neutral and in gear. I put transfercase in gear and tried to start it again. Now it cranks but will not start. I get spark and fuel. I'm not getting any codes. Where should I go from here? Thanks for any help you can offer.

Ok.

Compression
Fuel/air mixture
Spark
Right time
Right quantity

What is the missing element?

You state you have spark. Is the spark HOT, BLUE, and SNAPPY?

You state you have fuel. To the rail, how much pressure in psi? Are the injectors receiving power? Are the injectors receiving a firing impulse?

Just for fun, measuring between the battery terminals, how many VOLTS are present when cranking the engine?

joe_peters said:

Ok.

Compression
Fuel/air mixture
Spark
Right time
Right quantity

What is the missing element?

You state you have spark. Is the spark HOT, BLUE, and SNAPPY?

You state you have fuel. To the rail, how much pressure in psi? Are the injectors receiving power? Are the injectors receiving a firing impulse?

Just for fun, measuring between the battery terminals, how many VOLTS are present when cranking the engine?

Click to expand...

Thanks for taking the time respond. I'm sure glad I have your attention.

To answer your questions:

The spark did not look like I would expect a hot spark to look. It was definitely yellow, though it may have had a small blue center. I'm not really familiar with what I should be looking for though.

I can hear the fuel pump run, and fuel will squirt out of the test port. I don't have a tester for the fuel, so I can't tell you psi. I will get one if you think it is necessary.

How can I test if the injectors are receiving power and a firing impulse?

Voltage between the battery terminals when cranking is about 10.5 - 11 V. I did do a fair amount of frustrated cranking yesterday so I may have run the battery down a bit. Unfortunately I don't have a battery charger, but I will get one ASAP.

As a note, it sounded like it hit once while cranking.

Just to add another clue: I was cranking with one of the plugs out and the engine caught. It ran for a few seconds before I shut it down with the key. I put the plug back it and the most it would do is hit once.

That sounds like a plugged exhaust.

Pull a plug again and see if it will run with the one plug out.

hey bjorn,
crappy dilema. i know all my problems seem to arise in the winter months. but beyond cleaning up your terminals, checking your grounds, and probing a few areas for voltage, i dont really have anything for you. maybe light some incense and say a little prayer?




Joe-
what would cause an exhaust to plug up?

Physical crushed a pipe, CAT broken up inside, muffler baffles self-destructing.

been having problems since we went to rocks and valleys bjorn? your lower than me and i know my muffler got slammed. run over any ice chunks lately or climb any snow banks?

Sorry, for being slow to respond, school work got in the way this week.

Nope, this is the first issue since Rocks and Valleys. I haven't been playing in the snow or anything either.

I put a full charge on the battery and tried cranking with all the plugs in. It really tried to catch. It made just a little sound like it was starting, enough to really get my hopes up for a second. Then I pulled a plug and it just cranked. The pattern seems to be that the first time I crank it after letting it sit is when it tries to run or fires. The lowest the battery voltage dropped during a few seconds of cranking was 11.3V.

Also, a I'll add a little background, although I doubt any of it is relevant. A couple days before having this problem I replaced my transfercase drop with a SYE, added some small coil spacers, and slightly longer shackles. The problem began after I pulled into the garage to replace the zerks on the cv end of the rear driveshaft with some low profile/needle ones. The muffler was new this past summer, but the cat has been on since I bought the Jeep ~4 years ago. However, it has been a California Jeep up until this year and easily passed CA emissions this past summer.

Doesn't still sound like a crushed exhaust, does it? What should my next step be.

Thanks.

I just got it started. With pedal to floor it started right up. I let it run for a few seconds and shut it off. I was then able to resart it normally and it is idling in the driveway. My memory is that there is something different about a WOT start. Anyone know what happens different when you start with the pedal to the floor? Can anyone offer any theories as to what was going on? Thanks.

Edit: took it for a short drive, restarted it several times. Everything seems good. :dunno:

Pedal to the floor and then try to start puts the PCM in "clear flood" mode and it cuts off the firing impulse to the injectors.

joe_peters said:

Pedal to the floor and then try to start puts the PCM in "clear flood" mode and it cuts off the firing impulse to the injectors.

Click to expand...

Thanks for taking the time to help me out.

I guess it was just flooded. It sure fumigated the garage when it fired up. Haha. I feel kind of dumb, but it's all a learning experience. Anyway, I'm surprised by how long it stayed flooded. I would have guessed that if it sat for a day the fuel would have gotten past the rings.