I'll see your Jeep 'mechanic' and raise on 1988 MPI manual <g>.
There's was a fairly long section in there about the Cam sensor
failure in there dealing with the 87 recall. The wires from the
distributor were breaking and the diagnostic they give was no injector
pulse. There is also a separate ground for the injectors and one Jeep
mechanic at the local dealer was showing me where he had problems in
that big hulking connector on the firewall with that, so that's also a
good start, too. The cam sensor is easy enough to check - one pulse
per revolution of the engine. It's a Hall Effect switch just like the
Crank sensor.
I've dealt with the crapped out crank sensor and the limp home mode.
Boy! Is that ever an appropriate decription. It would start and idle
but anything much above idle it work buck and load down immediately.
I came home basically at idle playing with the gears all the way. I
think I got 1000 rpm max - sure did irritate the folks who got stuck
behind me. Even 5th gear at 1000 RPM makes the tortise look fast. I
guess if they know the crank angle from the CPS they could fire both
ignition and injectors for each pair of cylinders together but they
would still have to know where #1 was and I don't remember any unique
notch pattern on the flywheel ring that would tell them that.
On Thu, 12 May 2005 13:12:54 UTC Mike Romain <romainm@sympatico.ca>
wrote:
> I 'think' in another group some Jeep 'mechanic' insists that our renix
> will start and run without the cam sensor even plugged in?
>
> I had injector failure and it was a bad ground strap from the body to
> the engine. Some things can steal a ground, but not all. Once the
> starter is cranking, it can not leave enough juice to get around to
> everything and fire up the computer if it has bad connections.
>
> Mike
>
> Will Honea wrote:
> >
> > He says the fuel rail is pressurized and has no injector pulse - can
> > you think of anything besides the cam sensor that would inhibit the
> > injectors but not the spark? I assumed that the fuel pressure stayed
> > up during cranking. That long crank to start the Renix MPI 4.0 like
> > ours appears to be due to waiting for the #1 tdc pulse before putting
> > fuel to the cylinders. This also sounds a lot like the recall for the
> > '87 XJ/MJ where the Cam sensor leads were breaking off at the
> > distributor.
> >
> > On Wed, 11 May 2005 18:03:11 UTC Mike Romain <romainm@sympatico.ca>
> > wrote:
> >
> > > There is a ballast resistor out on the drivers side fender near the rad
> > > that controls the power to the fuel pump.
> > >
> > > Do you hear the pump hum when the key is first turned on?
> > >
> > > When was the last time the fuel filter was changed? It is on the frame
> > > rail just in front of the tank, drivers side.
> > >
> > > The pump also needs a ground which is supplied via the mesh strap from
> > > the rear of the head to the firewall. I test that by putting a booster
> > > cable from the battery negative tot he firewall to see if they start
> > > then.
> > >
> > > Mike
> > > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > > 88 Cherokee 235 BFG AT's
> > >
> > > sevensixtwo_fmj@hotmail.com wrote:
> > > >
> > > > Hey,
> > > > actually Help!
> > > >
> > > > Here's my symptoms:
> > > >
> > > > 1. Cranks fine
> > > > 2. Lots of good spark
> > > > 3. Timing was set TDC on compression stroke.. verified twice.
> > > > 4. Fuel Rail is pressurized
> > > > 5. Crank Pos Sensor functional (as far as we can tell)
> > > > 6. Map Sensor Functional (voltage too the sensor)
> > > > 7. Throttle Position Sensor is functional
> > > >
> > > > Big clue is the following and explains why its not firing:
> > > >
> > > > We stuck a Noid light on two or three injector plugs and
> > > > there's no pulsing to the injectors. This explains the lack
> > > > of starting. But WHY??? What could cause the fuel injectors not
> > > > to be pulsed.
> > > >
> > > > We haven't done a compression test but we've got a professionally
> > > > built long block so I'm not sure it needs to be done...
> > > >
> > > > Any thoughts or insight would be appreciated..
> > > > HELP HELP HELP
> > > >
> > > > Thanks
> > > >
> > > > James
> >
> > --
> > Will Honea
--
Will Honea
