ignition problem - cylinder related?

[hi_c]

1043206

89 YJ 2.5L 4-cylinder.



I go to the movies on friday. when I come out and hop in the Jeep, I turn the key and the starter is turning the engine, but it won't fire. I can tell it's not the battery cause the starter is flying (da-na-na-na-na-na-na, not slow). so I stop, give the gas pedal a kick, try again. same thing. then the third time, it starts right up. drove 5 miles home, no problem. put it in the garage, turned it off. tried to start it again. same thing. sometimes, it will fire on the first try.



So I replaced all the spark plugs, put in new plug wires. The dist.cap and rotor are less than a month old, so I just took them off and inspected them. They look like new, no cracks, erosion, or anything. I even changed the oil & filter and the inline fuel filter. All of this had no effect.



Could the problem be a bad cylinder that's not firing? The firing order is 1-3-4-2. Does that mean that it always starts on 1? what if 4 is bad and it tries to fire first, does the cam shaft spin and perhaps land on a new starting cylinder like a revolver and russian roulette? I've gotta buddy that owns a machine shop so I'm gonna get him to do a compression check on each cylinder. Should I replace the Dist.cap anyways?



HELP!

[addsig]

 

[MudderChuck]

1043214

Could be a whole list of problems. But one cylinder not firing, doesn´t often keep the motor from firing, just makes it start and run rough. It´s usually either spark or fuel when it doesn´t start. Been driving through any big rain puddles lately, a little to fast? Getting things wet will mess with the starting. Might take a look at the choke (carburated models) many times at the change of season they need a little adjustment. One good test is, when the Jeep has been standing for awhile, remove the air cleaner hold the choke open about and eigth of an inch pump the gas a couple of times and try staring with no gas pedal. It should pop over and try to fire even if it doesn´t run. This is a good indication if it´s fuel or spark. Timing can also make for hard starting. On TBI models, it´s usually in the ignition. And most times moisture somewhere.[addsig]

 

[hi_c]

1043216

I have the TBI fuel injection. I have gone through some rain lately, but not more than usual. And the Jeep stays in the garage over night. What else in the fuel system should I check? How can I tell if the ignition coil and module are still good? If they were bad, it probably would fail 100% of the time. I guess...? Thanks for your input and any other suggestions you have.

[addsig]

 

[MudderChuck]

1043224

When mine gets to starting hard, I pull a plug and look at the color. Full with black crud, means oil leaking into the cylinder. Black or grey OK. The next thing is start removing high voltage wires (mostly between the coil and distributor) and looking in the end of the boot for moisture. A bad or leaky coil cable will cause hard starting. Sometimes water will collect in the bottom of the disitributor under the mounting plate (blow out with air). Next thing is remove a spark plug boot, crank the motor and check the spark to ground (quarter inch gap from ground, using a screw driver as an extension out of the boot), check the color mostly orange, weak spark, mostly blue OK (be careful not to get to close to the metal with your fingers). Don´t know why exactly, but at the change of season many electrical thing seem to act up. Mine seemed to start better after running a load of injector cleaner through the gas tank. Chiltons has a section on fuel pressure test for the TBI. But like I said, could be a bunch of things, hard starts can be hard to nail down. A stuck PVC valve will cause hard starts and rough idle. A stuck EGR valve will cause hard starts and stalling.[addsig]

 

[hi_c]

1043322

Thanks, chuck. I'm gonna check the PCV valve today and put some injector cleaner in it. I haven't done that in a while. It was real hard starting today. I almost gave up. It took 10 or 12 tries before it rolled over, and even then it was hesitant. It was like it fired at 100 rpms not 1000 like it should and then it built up to idle speed, you know, hesitant. So that makes me think it's more fuel related. I think I can rule out the fuel pump or sending unit, because if it was bad, wouldn't it have trouble getting gas an highway speeds? See once, it's running, it's running good. No rough idle or stalling or anything. Weird. Let me know if you think of anything else. Thanks again.



hi_c

[addsig]

 

[hi_c]

1043352

Ok, So I took it to a diagnostic center and of course it started up everytime for them. They checked the Throttle body, all hoses, vacuums, electrical and said everything was fine. Of course. But, I noticed something... you know how we Jeepers are, we can hear every little foreign noise and want to find out what it is. Well, I know that ususally after you cut the Jeep off, you immediately hear a 1-second long electrical noise, almost like the Fuel injectors are spitting gas into the cylinder for the next time it starts. Well, that noise is not there when I cut it off. Is this common to all YJs? Is that what is happening, the fuel adding for the next time the jeep is started? That would explain why it starts when it's been recently driven, but not after it's sat for a while. I know that once it does crank, in the morning, when I give it lots of gas, it's fine for the rest of the day. I'm gonna get some f.i. cleaner and dump it in the tank when it gets low. Any other ideas are welcome. By the way, the PCV valve is good. I know you can pull it up when the engine is running and put your thumb over it and feel a vacuum. There was.

[addsig]

 

[Craig]

1043402

I had a similiar problem with my 93 YJ. The fuel pump was going. Take it into a garage and have them pressure test your fuel pump. When you shut off the jeep the pressure should remain in the line for the next time you start it. If your pump is going, that pressure will bleed off making it hard to start next time.[addsig]

 

[MudderChuck]

1043438

There is supposed to be a pressure valve on the fuel return. They check it by loosening the fuel line, to the injector, on the TBI models, it should squirt some gas when loosend, even after sitting. Like Craig said there is always supposed to be some pressure on the fuel lines. It is probably bleeding back through the pump or through the pressure valve to the return line. There is a special fitting that you can buy to check the fuel pressure, a refrigeration gauge or fuel pressure gauge will probably tell you whats going on quick.[addsig]