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1998 Jeep XJ, has no injector pulse. How do you diagnose if it is a PCM fault, or something else not allowing the PCM to do its job?

The following has been confirmed; Yes there is spark, yes there is 10.5V at the injector when cranking, yes there is 49psi fuel pressure when cranking, yes there are pulse voltage at the Cam and Crank sensors. No there are no codes or check engine light

Posted by Captain Corkyeye on


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  • 108 Answers

SOURCE: no spark at coil

check ignition pick-up coil and ignition module

Posted on Mar 31, 2009



  • 2 Answers

SOURCE: 1996 Jeep Grand Cherokee No Start

I would be thinking that there is a good chance that you need to be checking out replacing the computer, if you aren't getting any communication with the proper scan tool then the computer isn't communicating with anything in the vehicle...... I would have guessed first off that the ignition control module might be bad but that is obviously part of the computer also, I would be looking in that direction.

Posted on Sep 19, 2009



  • 306 Answers

SOURCE: jeep grand cherokee

Just trying to help. Jeep dealer won't tell you what code means? My guess would be in the intake system. MAF sensor? Air intake leak? I don't think its the pos. sensors because your engine would not run (been there done that). Your throttle is cable driven?

Posted on Mar 05, 2010


Robert Monigold

  • 390 Answers

SOURCE: Need a complete wiring diagram '90 jeep laredo 4.0

you can get a hanes book at any autoparts store.But you may want to check the tps also.

Posted on Jun 12, 2010

Nicolo Carlo Parazo

  • 2187 Answers

SOURCE: 2002 WG Jeep Grand Cherokee

The error P1130 and P1131 is for the fuel trim and lean fuel mixture respectively. This tells me that this may be an issue with the air fuel mixture or its reached its limits in compensating for the incorrect mixture. You could try to clean out the intake first using carb cleaner spray or tuner spray to clean out the intake and the MAF sensor which measures the air that comes in. Check also if there are leaks or gaps on the air duct found between the air filter and the intake manifold and the intake plenum. Leaks would cause the system to get an incorrect reading. If it were a faulty sensor you should get the error code for the sensor and you may have issues starting the engine up.

Check also the vacuum hoses which may be loose or cracked that needs replacing or refitting. This is also a common cause. I also do not rule out the possibility of the fuel sensors going or starting to go bad. The PCV may also need cleaning or replacing.

With all mentioned items go check first the leaks of the intake system and the vacuum lines as these are found to be common. Some leaks or cracks are minimal but is crucial to the sensors.

Posted on Jun 22, 2011

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2 Answers

Check gauges light on, Temp gauge at 0, vehicle wont start.

Could be connected, but could also be two different problems.
It could be something in the key switch, or a wiring problem. Or it could be a wiring problem with the temp gauge and something else causing the engine not to start.
Do you have spark and fuel pressure at the injectors ? And does the gas gauge work ?

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The engine will not turn over, crank senor maybe

MAYBE? It could be many other things too. Do you have spark, gas from the injectors, fuel pressure, does the engine turn (combustion), exhaust pressure. Start by scanning the computer, any codes to work with? Do you smell gas,Then try pulling the plugs, wet w/ gas? Maybe loss of spark. Checking for spark & to ck the fuel injectors require specialized equipment. I cant go any further unless you are equipped. Getting back to your original question, yes I've changed many crank sensors for no start problems. Have it ckd before you just throw money out the window. Good luck

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94 chrysler town and country stalls after getting to a normal temp but wont start back up till its cooled down.

The crank position sensor could be bad.Check the injectors & fuel pressure regulator with this test.Hold the gas pedal to the floor while you crank the engine.Does it start??If yes,the fuel pressure regulator is bad or you've got a internally leaking fuel injector.Let the engine idle,pull the vacuum hose off the regulator and see if gas is inside the hose or gas is seeping from the regulator vacuum port.If yes,the regulator is bad.You can shut the engine off,wait 5 minutes then pull all of the spark plugs.If a plug is wet with fuel,that cylinders injector is leaking.A bad ignition module or ect sensor can also cause a no start.You can do the following test when the problem is occurring.Remove the air intake hose from the throttle body,spray carb cleaner or starting fluid into the TB opening, reinstall the hose,try starting the engine. If it starts and runs for a few seconds then dies,you've got a no fuel problem. If it doesn't start at all,you've got a no spark problem.

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My Suzuki XL7, is pumping fuel but it won't start, what can I do to make it start?

Just because it pumps fuel doesn't mean there is enough pressure. If there is, then check for spark at the plugs.

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Where is the fuel pump cut off switch located on a 1997 geo prizm

why do you think it has this?
why not post symptoms
got zero fuel pressure cranking? or 30?
EFI runs large pressure or the injectors all FAIL.

we can work symptoms, not phantom , missing switches.
im not even going to look.

post the symptoms first. Example. 1.
does it crank y/n (yes)
does it start, no.
does it have spark on all cylinders, y/n
guess yes,
does it start and run on test fuel for 3 seconds?
ok , test fuel pressure next. (28psi is lowest on about all cars made)
which engine you have?
7AFE toy engine?

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1 Answer

Suzuki Aerio 2004, will crank over floods out tho. Changed Plugs and Boots. New baterry too. Can smell gas @ Tail pipe. Wants to fire-but just won't catch. Where do I start looking for the answers.?

what engine? 2.3 or 2.5L?
all cylinders flooding??? spark tips on ALL dripping in gas?
check spark at all spark plugs ( ALL not just ONE)
if spark is good.
this engine is chain cam, so it makes huge noise before death.
did it?, nah
ok, so connect any $9 scan tool, and scan it. (barrow /rent.?)

you crank it for 5 seconds, not less.
and as you crank the scan tool RPM shows 250 to300 rpm and fails to start, the RPM on the tool shows you that the crank sensor is working
now release the key and do not turn off
look for DTC errors. got P0340,355? or any other DTC
that decodes to bad CMP or CKP/
yes, BINGO, the scan tool told you why spark is dead, or way off

the PCM will report Cmp or CKP errors even 1 in 6 pulses.
the PCM runs monitors against these 2 full time. and will see it fail.
and report, it, let it tell why spark is bad.
say spark is good. and still floods.
1: engine compresssion over 150psi? W.O.T?
2: flooding , i pull the fuel pump relay and crank now.
starts and runs for 3 -5 seconds, yes, that is the flood clearing
so i then try test fuel, runs perfect now (no fuel pump) ???
runs for 3 second, each test fuel usage. well good motor, good spark.
what more do you want? sure to run
so you have either insane high fuel pressure. or injectors leaking
can and does happen.
the tests are all in the FSM under injector and pump testing.
i check fuel pressure first. as its a mandatory thing.....
to factory spec. for unsaid engine.
then i do a injector leak down and balance check.
ask if you get this far.....????

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2 Answers

93 tracer lost power on highway while driving, i checked the fuel pump switch in trunk then checked gas filter hose and cranked gas came out so not fuel problem then i checked to see if i have spark a

Clogged air filter ? Needs air into the engine also ,plus compression . Are the fuel injectors spraying fuel into the engine ? Try spraying starting fluid into the engine through the throttle plate and seeing if it starts then ? If it does ,fuel injector problems .

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1 Answer

1998 grand maquis crank no start no injector pulse as well as no ignition spark. Have changed crank sensor, cam sensor, fuel pump, pcm, injectors and still no start no voltage to sensors or injectors.

Car not starting or turning over indicates towards multiple possibilities. It can be issue with battery or weak battery. But if battery checks out ok, then it can be starter issue or faulty alternator or problem with low fuel pressure or no spark at spark plugs due to dirty spark plugs or faulty ignition coil or injectors getting cracked or dirty and needs to be cleaned.

To confirm the problem, the basic troubleshooting is required.

Click this link below and follow the troubleshooting:------


This will help.


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1 Answer

Jeep is hard to crank an when it does it runs rough for a few minutes until you rib it up then it runs ok but does not get good fuel milage, i replaced crank sensor,spark plugs,three fuel pumps and...

It sounds like there is a fuel leak. Most possibly internal to the fuel pump module. There is an o-ring above the fuel pump on the module that deteriorates and allows fuel to drain back into the fuel tank. It causes a host of problems including yours. Connect a fuel pressure guage, start the engine and watch the pressure increase to @49psi. Then shut off the engine and check the pressure drop. It should not drop bellow 20psi within 10min, and still have some residule pressure the following morning. If not then the o=ring will require replacing, Sounds like its been going on a while. worth a look!

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1 Answer

1990 Dodge Shadow cranks strong but wont turn over. Could it be the fuel pump relay. Doesn't seem to be a injector. Any advice

Yes the possibility in such cases can be the fuel or the spark . So if you think there is a stench of the fuel supply then the fuel pump must be checked out , if a calibration is done to confirm the fuel pressure.
Also once the fuel system is cleared the spark intensity must checked, check for HT coil , wires and plugs to be working in good order.

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