92 xj won't start

A

aolivett

NAXJA Forum User

Location

Centennial, CO

• Feb 13, 2011

• #1

92 jeep cherokee laredo won't start. it's the 4.0L. we took it in to all american 4x4 to get it diagnosed and they said fuel pump and battery. we did both of those as well as the fuel filter, cps, and ignition coil. before we replaced the fuel pump and battery and fuel filter, all american got it to run and it was running for a couple days then died again. we tested the spark and they are pretty good, good enough for a start i think. what else could it be?

 

A

aolivett

NAXJA Forum User

Location

Centennial, CO

• Feb 13, 2011

• #2

we also tried spraying starting fluid in the intake

 

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winterbeater

NAXJA Forum User

Location

Royal Oak, Michigan

• Feb 13, 2011

• #3

Compression! Check compression first before wasting any more money. Check for spark first...you have done that. Second, check for gas........spray start kind of verifies that is not the problem. Next pull the spark plugs and check for compression. Also, look at the plugs to make sure they are good. Likely, you checked or replaced the plugs already.

Again, check the compression.

 

Ecomike

NAXJA# 2091

NAXJA Member

Location

MilkyWay Galaxy

• Feb 13, 2011

• #4

New fuel pump could be bad, especially if they used a junk brand like Airtex. Have you checked fuel pressure?

 

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birchlakeXJ

NAXJA Forum User

Location

Melrose, MN

• Feb 13, 2011

• #5

1. Ensure fuel pressure is correct at the fuel rail. WITH A GAUGE

2. Quality of spark. You are looking for a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark, which may not be strong enough to start the engine.

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Feb 13, 2011

• #6

All good advice.

Your spark needs to be HOT, BLUE, and SNAPPY. Yes, an engine CAN run with a crappy spark, if the engine is in good condition, the fuel is top notch (not ethanol or winter blend).

Check the fuel pressure, and check the firing impulse of the injectors--you don't have to have a NOID light ($4-$8), a very good DVOM will read the firing pulse, like a Fluke 88 ($350+).

You can check for power to the injectors with any meter/test light. You need an ANALOG meter to test the synch sensor in the distributor.

 

A

aolivett

NAXJA Forum User

Location

Centennial, CO

• Feb 14, 2011

• #7

how do you check compression? we checked fuel pressure and it is good.

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Feb 14, 2011

• #8

Compression gauge.

Should be able to rent one at a chain parts store.

 

Ecomike

NAXJA# 2091

NAXJA Member

Location

MilkyWay Galaxy

• Feb 14, 2011

• #9

If it was running for a couple days after all that prior work, before it died again, why jump to a compression check? Why not check fuel first? If it has spark, that confirms the timing chain is not busted I think?

 

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webbjeep

NAXJA Forum User

Location

Bel Air, MD

• Feb 14, 2011

• #10

Does it "start" at all, mine cranked breifly then died. Found out it was a $6 fuel pump relay. Just a thought, usually its something small and goofy.

 

Ecomike

NAXJA# 2091

NAXJA Member

Location

MilkyWay Galaxy

• Feb 14, 2011

• #11

webbjeep said:

Does it "start" at all, mine cranked breifly then died. Found out it was a $6 fuel pump relay. Just a thought, usually its something small and goofy.

Click to expand...

Good point!!! I suspect a lot of fuel pumps get replaced before their time due to connection problems, like dying relays. Both my 87 and 89 acted like dead fuel pumps in the last 2 years, turned out to be very old, not so good connections from the relay to the pump pig tail connector to the pump/body ground. But in his case (OP) he said he had fuel pressure and no start as I understand.