Car was overheating and spitting out coolant, so i had my cracked radiator sealed, but this was after the temp gauge pegged. So i then found out that i had a blown head gasket and a cracked head. Had them replaced. Then right after, the waterpump blew and leaked down into the opti and i began having a misfire/stumble. The waterpump was replaced, plugs, wires, and opti all replaced. The stumble was still evident below 2000 rpms. Found the misfires to be in the 7th and 8th cylinders. Replaced the injector on on the 8 cylinder and left the 7th because it seemed fine. Fired it up and it drove around great. Fired it up again and the computer tossed the same code before for injector misfire, yet the car was running great.

I have had the problem with startin the car up. When i start the car it will rev up then spudder and die out. Therefore i have been giving it 2 or 3 cranks to the ON position and then it fires up and runs fine. Could this problem with the start be related to the misfire. The line from the fuel pump is only getting around 20 psi when it should be getting 40+. Is this a definate bad fuel pump? I replaced the IAC and it fixed my problem for nearly two days and it went back to the faulty start up. Any ideas? Any dead give aways that im missing other then the pressure being bad? Fuel filter? FPR?


Any help would be glady appreciated

 

TTT anyone?!?! Can the misfire code that is being tossed be related to the fuel pump due to low pressure...

 

Well I'm gona chime in here and first say you have a problem with your statement about injector misfires. The PCM will not know if there are occasional misfires caused by injectors. If your refering to the misfire counters, that monitors the rotational speed of the crankshaft and will detect misfires in a cylinder. The only injector fault I see for a 96 is the control circuit fault. DTC 1200.

If it turns out you have an injector fault, you can mention that in the answer. I think you should address the fuel pressure problem. It's much too low and either the pump is bad or something is bleeding off pressure. Other than a hole in the fuel line, either the the FPR is bad or the injectors are sticking open. BUT if the injectors where sticking, it would flood, probably not run from too much fuel in the cylinder and the oil would be contaminated.

If the FPR doesn't have a hole in the diaphragm, that is the vac hose isn't wet and will hold vacuum, chances are it will not allow the pressure to drop down that low. So that leaves you with one last choice. I guess if the sock on the pump in the tank where clogged, it would do the same thing?????

Fix your pressure problem then go from there.

 

if ur only getting 20psi from the pump i think its evident that its prolly ur pump, im not saying 100% it is but thats where u should start

i was getting random misfire codes when my pump started to die and most of ur symptoms are the same

just gonna ask , how old is ur fuel filter?? when was it last changed

 

I have had the car since 49K and it has 86K on the clock....I haven't changed the fuel filter since i bought the car... should i start there and then move towards the pump?

 

start with the filter and work from there,

check to c if teh relay is getting power
check to c if the pump is getting power (there is a wireing harness under teh car near teh driver rear tire)
test the FPR
when u turn the key to the on position (not start) can u hear the humm of teh pump ? also do u hear the relay click ? (96 i believe teh relay is right under teh kickpanel on driver side) just listen for it. it will click off after about 2 seconds
if all is good i would say its the pump
ur car is experiencing the same problems my car had when the pump went

good luck

bobbyd

 

If you have 20psi, the pump is running and the relay is on.

 

i replaced the fuel filter... no help with the miss but it did seem to help my idle somewhat.... its staying around 800-1000 instead of dropping down to like 400/500...is there anyway to mount an electronic fuel pump in the engine bay like old carbeurated motors? seems like it would be easier than replacing the pump in the tank if i could find a way to by-pass it

 

u can buy an inline fuel tank but i believe u stll have to mess with the pump in the tank anyways so minds well change that one ,

did u check ur fuel pressure again ? after the filter change?

 

might be a shot in the dark but i have a 94 cherokee that was having the same sorta issues and turns out it was the CPS (crank shaft position sensor)
Might check that, i had multiple cyc missfire on my 96RS and after further checking into i had a spun bearing on the #6 Rod which caused all kinds of problems so i would start small and then work your way up. Did you erase your PCM before installing the new injectors? I know the computers will save the settings of sensors and when you install the new ones the parimaters are set and you have the same problem. I am not sure if it does that for the injectors but it is worth the research. GOOD LUCK

 

i took it to a dealership where a guy that i know knows a guy and he hooked it up got a GM 2 scanner or some ****.. it was huge probably like 6 inches by liek 10 inches.. and he ran through it and was doing different tests, turning off injectors.. he ended up saying that the left side was getting 40% more gas than the right side trying to create a balance... he'd said he'd get back to me tommorow

 

so after overheating and pegging on the temp gauge... i was left with a cracked radiator, a blown head gasket, and a cracked head. had all of these fixed and then the waterpump went, had that replaced and then realized the optispark had gone. pulled the waterpump back off and replaced the opti. changed plugs and wires and two oxygen sensors and ended up with a missfire. turns out that the guys who did the radiators, head gasket, heads, waterpump, and opti left a vacuum leak due to hooking them back up wrong. had a leak in my EVAP. Had that fixed and then had to replace my fuel filter and pump assembly also. Yea... i just took a beating...but the vacuum leak ended up being my problem for the misfire.