89 yj crank no start

I have an 89 YJ 2.5 with a crank, no start issue. Has spark and injector signal, so I presume not a crank sensor or ecm problem. Did a compression test...3 cyls were 130-135 #4 cyl was 120, so thats an issue, but I wouldnt think it would cause it not to start. Fuel pressure is around 15psi with the key on, and about 22-25 when starting. That leaves me thinking bad injector, but was wondering if there was something I missed. It will to start with starting fluid.

 

Welcome @Vd2kilcm ...since you did the compression test whats the condition of the spark plugs? Perhaps a fresh set and wires would be a start even though starting with starting fluid makes one suspect fuel delivery or injector.

 

Spark plugs are new, and wires and cap look fairly new. I'm really leaning towards the injector, even though thats supposed to be new as well.

 

Per AllData compression for the 2.5 should be between 155-185 with a 30psi variance between cylinders.

While yours is a little low it wouldn't cause a no start issue.

Fuel pressure is good.


If it was a bad injector it should still start and run rough or at least act like it wants to start.

 

Every once in a while, it'll act like it wants to catch, then sputter out. Never longer than 2 or 3 seconds. Not knowing what the specs were, compression seemed a little low to me too...I'm used to seeing it in the 140-160 psi range for most vehicles. The low pressure on #4 bothers me more, though. I'm really leaning towards a clogged injector, even though its supposedly new.

 

Pull the injectors and the injector rail off the engine, place each injector into a clear plastic water bottle.
Have someone crank the engine so you can watch each injector pulse, if there is one that is clogged or not functioning you should be able to see it.

 

My $0.02 says fuel pump, especially a 31 year-old one (assuming it’s the original).
That or clogged fuel filter. Either one, or both, could give an intermittent fuel pressure reading that is within spec, then die off (the 2 or 3 second sputter-and-die thing). I’ve seen it wreak havoc while diagnosing other things. Maybe start with the filter??

 

Can't...it's TBI, and the injector is integral with the throttle body.

 

Could be, but it's both a new filter and a new fuel pump. Pressure stays steady while cranking, can't tell while its running though, cause it won't stay running long enough.

 

Ok, update...new fuel injector and o rings. The old one had a crushed strainer that was installed upside down, and was missing the bottom o ring. Fuel is definately making it there...builds over 20 psi while cranking and I can see fuel hitting the throttle plate. Just not sure if its its en, cause it still tries to crank with starting fluid. I would assume the crank sensor is still good, because its its getting fire. Could it still be intermittently bad, though? Or perhaps a vacuum leak?

 

How strong was the spark, and where did you take it? Could be weak, did you check it every plug wire or just at the distributor? With lower compression and perhaps weak spark, hard starting is common. Also, how old is the fuel? When was the last time it ran, recently? If so, search your memory for anything unusual the last time it ran, might jar loose an answer. One more thing, when you say crank with ether, you mean fire, start, right? I'd suspect the TBI has a plugged passage. How much fuel are you seeing at the plate and under it?

 

It will start with ether, and I can keep it running if I time the sprays just right. I can see the injector spraying fuel onto the throttle plate, though it seems like maybe not as much as should be there. Just changed the injector, and ran the fuel pump without the injector installed. Supply seemed ok, and it would build pressure if I held my finger over it. Disconnected plug wires from the plugs, and checked each cylinder...all were strong.

 

You could get a fuel pressure reading by setting up a fuel pressure gauge. Starting it up with the ether to get a reading.

 

Already have. Get around 15psi with pump on, not cranking. Get around 20-25 psi while cranking. Not sure about running...hasn't stayed that way long enough.

 

I am thinking that a weak coil would allow the engine to run with the ether spray and not on pump gas. Although bad gas could be an issue also. So check the coil condition and add some fresh gas. Sometimes you got to cover all the bases.

 

@Jim Beam got a point about bad gas. Didn't see any mention of this YJ running in your post... you might have a tank of old gas