1990 jeep cherokee no start

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spydey - 01 May 2006 18:38 GMT

Hey guys,

I've got a very frustrating problem here. Customer brought in a 1990
Jeep cherokee limited, 4whldrv, automatic. We replaced the engine with
one from a 1996. All the appropriate electronics were switched from
the old engine to the new including, distributor, cap, rotor, coil,
CPS, flywheel, intake and exhaust, all injectors (already on old
intake). The problem is we now have a no start/no spark condition.
This swamp is common at our shop, (newer 4.0L into older jeep) and
always goes off without a hitch. This is the first time I've run into
this. We've replaced the CPS, coil and ignition module check out O.K.,
Distributor checks out. We even put all the suspect parts into another
jeep and they worked fine. The computer has also been replaced but to
no avail. Any input would be appreciated. Thanks.
Jesse

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Jo Bo - 02 May 2006 01:13 GMT

That leaves wires! Check all the grounds that are on the passenger side
bolted to the block.

JoBo

> Hey guys,
>
[quoted text clipped - 11 lines]
> no avail. Any input would be appreciated. Thanks.
> Jesse

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spydey - 02 May 2006 01:15 GMT

You'd think so wouldn't you. However, I did check all these and the
grounds are great. Turns over via starter with authority.

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spydey - 02 May 2006 20:28 GMT

NEW INFO, fuel pump relay does not activate on cranking. When we
jumper the ballast resistor wires it chatters like crazy.

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spydey - 03 May 2006 01:56 GMT

K....injectors aren't firing. Can manually operate relay to activate
pump but when cranking the injectors won't pulse or let fuel through.
Sounds like CPS again, doesn't it?

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spydey - 04 May 2006 17:25 GMT

GREAT NEWS!!!!!!!!! Problem solved. You're not going to believe it
but it all comes down to wiring. (which I suspected in the first place
but thought I had eliminated that). I went back into the harness and
started checking wiring. I realized that when I was checking the
ground wires inside the wire loom that I missed about a 18 in section
just after the main splice on the firewall, engine side. They looked
good but decided to investigate further. Upon a more thorough visual
inspection I noticed two little pin holes where someone had apparantly
probed the wires at one point in time. Remembering that the customer
had told me he had submersed the jeep past the windsheild in soupy
water at one time I decided to remove the covering on the
wires.......They literally fell apart.

So....it all comes down to a bad ground. It was something simple but
hidden.

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