1994 Jeep Wrangler engine cutting out above 55

Tiny
SCOTTPAFF
  • MEMBER
  • 1994 JEEP WRANGLER
  • 2.5L
  • 4 CYL
  • 4WD
  • MANUAL
  • 190,000 MILES
Has power in 1rst thru 3rd. Cuts out above 55 in 4th and 5th. When you let off the gas it runs fine again. Tested fuel pressure and only getting 30 lbs. Is this a fuel pump or pressure regulator?
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Thursday, July 23rd, 2015 AT 6:23 PM

5 Replies

Tiny
CJ MEDEVAC
  • EXPERT
THIS MAY NOT BE THE FIX, BUT IT COULD HELP.

REGARDLESS, IF IT AIN'T BEEN DONE AS PER SCHEDULED MAINTENANCE, OR IN FOREVER!

CHANGE THE FUEL FILTER

IT MAY BE WAY PAST DUE!

RETURN WITH NEWS

THE MEDIC
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Friday, July 24th, 2015 AT 2:28 PM
Tiny
SCOTTPAFF
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Forgot to mention I changed filter before I give it a pressure test. That was my first thought also.
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Saturday, July 25th, 2015 AT 5:33 AM
Tiny
CARADIODOC
  • EXPERT
Fuel pressure spec is 31 psi, rising to as much as 41 psi with the vacuum hose removed and plugged from the pressure regulator. If there's no symptom in the first three gears, this suggests the cause is load-related. It's very rare to solve a running problem on a Chrysler product by replacing the fuel filter, however, there are problems with the pickup screen in the tank collapsing and blocking fuel flow, but that usually occurs when the largest volume of fuel needs to flow, which is during coasting.

The MAP sensor responds to load and would be a good place to start. First check the other hoses for vacuum leaks. You can watch the signal readings on a scanner too, but very tiny changes that we can't discern result in big changes in the fuel metering calculations, so it's hard to tell what's normal and what's suspect. The Engine Computer will accept any voltage reading between roughly 0.5 and 4.5 volts, even if it's wrong, The voltage has to be really wrong to go outside that range. That's what sets a diagnostic fault code.

Have you checked yet for diagnostic fault codes?

This reminds me of an intermittent problem I chased on my '88 Grand Caravan for a year and a half until it finally failed completely. It acted exactly like a dead accelerator pump in a carburetor, but only on real hot days, and then only at anything above 1/4 throttle. Turned out to be a failing ignition coil. My guess is higher spark voltage was needed under higher load, and the coil was breaking down internally or arcing internally at those higher voltages.
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Tuesday, July 28th, 2015 AT 1:57 AM
Tiny
SCOTTPAFF
  • MEMBER
Parts store wanted $80 bucks for the exact same fuel pump online I got for $12.50. Same brand and all. I just had to wait 3 days for mail to bring it. Put it in and all is well. I have seen some manuals that have said the lowest pressure needed was 31 and 41 both. In my case 31 pounds of pressure didn't cut it. I'm gonna say that the manuals that say 41 to 51 is the correct amount needed. Thanks for your help. Back in the trails again.
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Thursday, July 30th, 2015 AT 11:56 AM
Tiny
CARADIODOC
  • EXPERT
Have you measured the pressure with the new pump? My Grand Caravan calls for 50 psi, but it runs perfectly fine down to 20 psi. Did the pump come in a new housing or did you have to transplant a pump / motor into the old housing?
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Saturday, August 1st, 2015 AT 10:03 PM

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