1990 Jeep Cherokee LTD no start/no spark
 

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

1990 Jeep Cherokee LTD no start/no spark
 

asd relay or efi main? If you scan it do you see cranking rpms.
> wrote in message
ups.com...
> 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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1990 Jeep Cherokee LTD no start/no spark
 

1990 Cherokee. No ASD relay.

1990 Jeep Cherokee LTD no start/no spark
 

The 90 had a Renix computer system, the 96 has a Chrysler one. You need
the computer and harness from the 96 to get things going.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Shep wrote:
>
> asd relay or efi main? If you scan it do you see cranking rpms.
> > wrote in message
> ups.com...
> > 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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> http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
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1990 Jeep Cherokee LTD no start/no spark
 

No we don't. We used ALL of the electronics from the Bendix system.
There are absolutely NO 1996 electronics on this engine now. This is a
swap we've done multiple times and never had this problem. As long as
all the electronics are swapped over from the old engine it works fine.
This problem is not because of incorrect electronics.

1990 Jeep Cherokee LTD no start/no spark
 

Read that wrong....

How is the wire mesh ground strap from the rear of the head to the
firewall? If that is ratty, it will cause a no spark.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

spydey wrote:
>
> No we don't. We used ALL of the electronics from the Bendix system.
> There are absolutely NO 1996 electronics on this engine now. This is a
> swap we've done multiple times and never had this problem. As long as
> all the electronics are swapped over from the old engine it works fine.
> This problem is not because of incorrect electronics.

1990 Jeep Cherokee LTD no start/no spark
 

It's brand new and the connection is good

1990 Jeep Cherokee LTD no start/no spark
 

spydey wrote:
>
> It's brand new and the connection is good

My 88 has a ballast resistor on the fuel pump. I was told if this
doesn't work, the computer won't send a spark. Maybe the connection got
knocked?

The resistor is out on the driver's side fender on ours and is a ceramic
rectangle type.

Does the distributor have a ground? I have seen rust interfere with a
distributor signal.

There might be one other computer control ground on the inside firewall
just above the gas pedal. I am not sure what that one runs, but the
engine won't go without it. The YJ's ground the fuel pump in that area,
don't know about the Cherokee.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

1990 Jeep Cherokee LTD no start/no spark
 

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

1990 Jeep Cherokee LTD no start/no spark
 

I would be looking at the starter relay for a punky connection next I
think. If it isn't sending enough voltage on starter bypass to the
pump, maybe the coil also isn't getting enough.

The green wires I think are the ones to clean.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

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