Hard starting Cherokee

My buddy has an '89 Cherokee, inline 4.0L. When he starts it he has to crank
it for a good twenty-thirty seconds before it catches every time, hot or
cold. He says that it runs fine other than that. I've suggested checking
fuel pressure while cranking and after shut-down to see if it's a bad pump
or regulator. Any other suggestions I could toss his way?

I have the same problem, in the same Jeep, with the same engine, except mine
only takes about 15 seconds.

Would love to know why..

carl


"SBlackfoot" > wrote in message
.. .
> My buddy has an '89 Cherokee, inline 4.0L. When he starts it he has to
crank
> it for a good twenty-thirty seconds before it catches every time, hot or
> cold. He says that it runs fine other than that. I've suggested checking
> fuel pressure while cranking and after shut-down to see if it's a bad pump
> or regulator. Any other suggestions I could toss his way?
>
>

He should clean the electrical contacts on the TPS and CPS with a spray
contact cleaner. An electrical spray is best, but WD40 works in a
pinch. The TPS is on the throttle body and the crank position sensor
plug is just behind there on top of the intake manifold. Both of these
get dirty with age and affect the starting speed. A new fuel filter
that is located on the frame rail in front of the gas tank also can do
wonders for a slow start.

And then Cherokees of that era are just long starters when cold anyway.
The CPS has to see a signal from the flywheel before it sends spark.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

SBlackfoot wrote:
>
> My buddy has an '89 Cherokee, inline 4.0L. When he starts it he has to crank
> it for a good twenty-thirty seconds before it catches every time, hot or
> cold. He says that it runs fine other than that. I've suggested checking
> fuel pressure while cranking and after shut-down to see if it's a bad pump
> or regulator. Any other suggestions I could toss his way?

> My buddy has an '89 Cherokee, inline 4.0L. When he starts it he has to
crank
> it for a good twenty-thirty seconds before it catches every time, hot or
> cold. He says that it runs fine other than that. I've suggested checking
> fuel pressure while cranking and after shut-down to see if it's a bad pump
> or regulator. Any other suggestions I could toss his way?


For the record we made progress on the hard-starting problem. For whatever
reason he pulled his fuel rail and injectors only to break a few of the
injectors and kink the fuel rail. Injectors, fuel rail, and pressure
regulator from a junkyard truck seems to have cured the problem.

Interesting, thanks for the update. Does the regulator also have the
anti-drainback valve in it?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

SBlackfoot wrote:
>
> > My buddy has an '89 Cherokee, inline 4.0L. When he starts it he has to
> crank
> > it for a good twenty-thirty seconds before it catches every time, hot or
> > cold. He says that it runs fine other than that. I've suggested checking
> > fuel pressure while cranking and after shut-down to see if it's a bad pump
> > or regulator. Any other suggestions I could toss his way?
>
> For the record we made progress on the hard-starting problem. For whatever
> reason he pulled his fuel rail and injectors only to break a few of the
> injectors and kink the fuel rail. Injectors, fuel rail, and pressure
> regulator from a junkyard truck seems to have cured the problem.

On Sat, 5 Mar 2005 14:46:34 UTC Mike Romain >
wrote:

>
> Interesting, thanks for the update. Does the regulator also have the
> anti-drainback valve in it?

Mike, I pulled the old pump apart when I swapped it out in the 88. In
that one, the drainback was essentially a ball that the pump pressure
opened with a small spring to close it when pressure was off from the
pump. It was in a housing that was inserted between the outlet of the
pump and the outlet feed line.

The regulator is supposed to keep the pressure up so that it closes
off the return line when pressure drops below 30 pounds but reading
the MPI manual for the 88, it looks like the limit on that is closer
to 20 pounds - the MPI manual calls for no less than 19 pounds in the
fuel rail after 10 minutes bleed time.

The new pump I put in (universal replacement type) had the check valve
inside the pump housing cap so I put the old external check valve on
as well. I the process, I found a universal check valve for drainback
at the parts house. The (old) counter guy said it was for GM cars and
went on the inlet side of the fuel filter. He carried it for pumps
that worked but bleed back - much cheaper and easier than dropping the
tank and replacing a perfectly good pump jsut because of a $0.25 ball
valve! FWIW, I just checked mine after setting for 2 days - 14
pounds.


--
Will Honea

Will Honea wrote:
>
> On Sat, 5 Mar 2005 14:46:34 UTC Mike Romain >
> wrote:
>
> >
> > Interesting, thanks for the update. Does the regulator also have the
> > anti-drainback valve in it?
>
> Mike, I pulled the old pump apart when I swapped it out in the 88. In
> that one, the drainback was essentially a ball that the pump pressure
> opened with a small spring to close it when pressure was off from the
> pump. It was in a housing that was inserted between the outlet of the
> pump and the outlet feed line.
>
> The regulator is supposed to keep the pressure up so that it closes
> off the return line when pressure drops below 30 pounds but reading
> the MPI manual for the 88, it looks like the limit on that is closer
> to 20 pounds - the MPI manual calls for no less than 19 pounds in the
> fuel rail after 10 minutes bleed time.
>
> The new pump I put in (universal replacement type) had the check valve
> inside the pump housing cap so I put the old external check valve on
> as well. I the process, I found a universal check valve for drainback
> at the parts house. The (old) counter guy said it was for GM cars and
> went on the inlet side of the fuel filter. He carried it for pumps
> that worked but bleed back - much cheaper and easier than dropping the
> tank and replacing a perfectly good pump jsut because of a $0.25 ball
> valve! FWIW, I just checked mine after setting for 2 days - 14
> pounds.
>
> --
> Will Honea

So the regulator has or controls the check valve for the return line
then?

Ok that make sense and and I like the inline valve idea. Thanks.

I guess a clamp crimp on a flex line would isolate which way the gas was
leaving.

Our 88 is only a bit slow, it doesn't bother my wife who drives it the
most. I find it slow compared to my carb CJ7 that fires sometimes
before you hear the starter turn.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

On Sun, 6 Mar 2005 17:08:30 UTC Mike Romain >
wrote:

> Will Honea wrote:
> >
> > On Sat, 5 Mar 2005 14:46:34 UTC Mike Romain >
> > wrote:
> >
> > >
> > > Interesting, thanks for the update. Does the regulator also have the
> > > anti-drainback valve in it?
> >
> > Mike, I pulled the old pump apart when I swapped it out in the 88. In
> > that one, the drainback was essentially a ball that the pump pressure
> > opened with a small spring to close it when pressure was off from the
> > pump. It was in a housing that was inserted between the outlet of the
> > pump and the outlet feed line.
> >
> > The regulator is supposed to keep the pressure up so that it closes
> > off the return line when pressure drops below 30 pounds but reading
> > the MPI manual for the 88, it looks like the limit on that is closer
> > to 20 pounds - the MPI manual calls for no less than 19 pounds in the
> > fuel rail after 10 minutes bleed time.
> >
> > The new pump I put in (universal replacement type) had the check valve
> > inside the pump housing cap so I put the old external check valve on
> > as well. I the process, I found a universal check valve for drainback
> > at the parts house. The (old) counter guy said it was for GM cars and
> > went on the inlet side of the fuel filter. He carried it for pumps
> > that worked but bleed back - much cheaper and easier than dropping the
> > tank and replacing a perfectly good pump jsut because of a $0.25 ball
> > valve! FWIW, I just checked mine after setting for 2 days - 14
> > pounds.
> >
> > --
> > Will Honea
>
> So the regulator has or controls the check valve for the return line
> then?
>
> Ok that make sense and and I like the inline valve idea. Thanks.
>
> I guess a clamp crimp on a flex line would isolate which way the gas was
> leaving.
>
> Our 88 is only a bit slow, it doesn't bother my wife who drives it the
> most. I find it slow compared to my carb CJ7 that fires sometimes
> before you hear the starter turn.

The regulator has a diaphram/spring operated valve that is set to
about 40 psi by the spring which is offset to 31 pounds when vacuum is
applied (poor man's aoutomatic choke ??) but like most hydraulic
regulators the spring is set up to just close at the 40/31 psi. The
spring doesn't create enough pressure to get a really tight seal until
the fluid pressure drops a little below the 'closed' point - it makes
contact with zero force at that pressure, so you get a seep. It's not
really a check valve in the return line, just the nature of the
regulator.

--
Will Honea