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#1
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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? |
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#2
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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? > > |
#3
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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? |
#4
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> 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. |
#5
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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. |
#6
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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 |
#7
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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 |
#8
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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 |
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