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89 No Start! HELP! Getting Fuel and Spark

tirogers

NAXJA Forum User
Location
skandia mi
This forum has helped me MANY times!! Thank you ever one! Usually if i search long enough, i can find my solution with out having to post a new topic...well not this time! Hopefully this post will also help other!

This is my 2nd jeep Cherokee and this one is driving me nuts!

It had a 1990 rebuilt engine put in by the previous owner. It was running rich so i put it on the garage and proceed to check the map sensor to see if it was functioning property. Partially through the test I tried to restart the engine and it just cranks and crank and cranks and now I am stumped.

I noticed the crank position sensor had come unplugged as I was messing w/ the map sensor and was sure that was the solution....long story shot It was not!

I replaced the crank sensor about a month ago...so im sure that cant be it...also it it getting spark

Thought maybe I was low on gas...also not the problem

I am getting spark and good fuel pressure to the rail, newer plugs and wires too.

Is there something I'm missing? Or do I have an electrical bug that is gonna be hard to track down? Can someone point me in the right direction?

What else should i check?

:dunno:
 
No matter how sure you are, check that CPS again... especially if it was a bargain aftermarket one!

Have you checked fuses? Maybe screwing around with the harness/plugs you shorted out a wire against something and blew a fuse?
 
checked all the fuses under the dash, there is none under the hood right? I replaced the 4 relays by the battery with new ones. I will check the crank sensor right now, just have to dig up the test procedure again. And yes it was a cheap aftermarket one! Do you know the test procedure off hand?
 
Test#1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the cps and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If it's out of that range by much; replace it. (* - Note: HO engines are measured from the B & C connectors and should have near zero ohms.)
Test#2 - You'll need a friend to help ya with this one.
Set your volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your friend cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.




going to do it now
 
was it a good blue snapping spark at the spark plugs and did you test fuel pressure or get a good stream of fuel to shoot out of the schrader valve/fuel rail?

another things to check is that you reconnected the MAP vacuum line onto the MAP vacuum port, not the screw/stud of the bracket that holds the MAP. i did this on my 89 when in the dark.

lastly, recheck the cps wiring harness. if it was loose enough for it disconnect while working on the MAP, it could be making bad contact when connected.
 
yes spark is strong, it fired right up every time until i started messing with it running rich

i have swapped in another map sensor out of my other jeep with no results....yes the vacuum is hooked up correctly

fuel pressure is good, i get a steady strong stream out of the schrader valve when cranking it over

have also double and tripled checked the cps hook ups
 
wiggle the cps connector while some ones turns the engine over.

check that the plugs are not fouled with gas. do you smell gas? if its not starting and you have fuel pressure, it will have a heavy gas smell.

where are you checking for spark? at the spark plug or at the cap?

recheck the MAP vacumn connection at the MAP and on the throttle body. on the throttle body, there are two ports on the rubber grommet where the vacumn lines goes, one of the ports is blocked while the other port goes through to the throttle body.
 
wiggling the cps sensor didn't do any thing, tried that previous to posting and again just now

there is a gas smell but not tooo strong, just pulled 2 plugs and they look good, also had gas on them

checked spark at a plug w/ a spark plus tester thingy

as for the map sensor vacuum line i can not seem to trace where it goes it appears to rundown by the tranny fluid fill/check then under the radiator tank thing in by the passenger fire wall, to a connector where there is place for 2 lines to plug in but only one is, form there my hand can not reach....does this sound incorrect?


damn this is upsetting!
 
last night when this started, as i would crank the key it kinda sounded like it wanted to start as long as i kept the key cranking, also some time but not often it sound like it wants to start...but not for long only a split second
 
wiggling the cps sensor didn't do any thing, tried that previous to posting and again just now

there is a gas smell but not tooo strong, just pulled 2 plugs and they look good, also had gas on them

checked spark at a plug w/ a spark plus tester thingy

as for the map sensor vacuum line i can not seem to trace where it goes it appears to rundown by the tranny fluid fill/check then under the radiator tank thing in by the passenger fire wall, to a connector where there is place for 2 lines to plug in but only one is, form there my hand can not reach....does this sound incorrect?


damn this is upsetting!

yes, thats not correct. the MAP vacumn lines runs from the bottom of the map to the side of the throttle body. the vacumn line is only about a foot long from the map to the throttle body. at least this is the way it is on my 89 with a 5-speed(no trans fill/dipstick).
 
i would take the spark plugs out and hold a lighter to the electrode to burn off any gas. if you have some spare plugs, throw them in. the plugs your using are saturated in gas.
 

halfway down the page is the map sensor, its located on the firewall behind and above the valve cover, but the vacumn line runs to the throttle body. on the left side of the throttle body there is a rubber grommet that it gets connected to.

if you didnt mess with the vacumn line routing, ii dont think its your no start problem. my 89 starts with the map line disconnectd but runs and idles terrible. my guess would be fouled plugs, bad cps wiring harness, or possibly disconnected ballast resistor wires.

also check the ground strap. it may have been knocked loose or is crumbling apart as it is next to the map sensor.
 
battery bis new a month ago, plenty of volts 13.8 i just checked plus i have a charger hooked up to it from all the cranking, it cranks over strong
 
ground strap appears good, ill try and takea pics so some one can show me where the map vaccume plugs into, i found a place on the intake where the previous owner pluged one of the 2 holes, maybe this is it?


possibly disconnected ballast resistor wires.......this the thing between the coil and battery with lotsa wires?
 
battery bis new a month ago, plenty of volts 13.8 i just checked plus i have a charger hooked up to it from all the cranking, it cranks over strong

Good.

Do you have a fuel pressure gauge so you can test the actual pressure? Volume and pressure are two different issues.

BTW, did you know that the fuel pump gets its power from 4 different systems? During priming, it comes through the B latch relay (aka ASD relay), during cranking it comes through the starter relay, during normal running it is through the fuel pump relay and the ballast resistor, and when at WOT it is powered through the oxygen heater relay. Good thing the Jeep engineers didn't make things too complicated.
 
no i dont have a fuel pressure guage, it sounds wierd to me the jeep would start fine when i pulled it into the garage to try and figure out the rich running condition, i then started it several times testing the resistance on the map sensor, and bam now no start....
 
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