91 YJ won't start


New Member
Feb 3, 2024
i am very new here, but the question is very old. i bought 91yj 4.0, auto, and restored it. Now i tried to start. it cranks very good, there is fuel and spark plug, but nothing, not even one fire. I did removed the distributor, and i am not sure if i installed it corectly. But even not, it shoud at least fire couple times, but nothing.
Any advise ?
Poland?? seriously? Love to see some pics of off roading there. There is 2 TDC's, one compression stroke and the other valve overlap during the intake/exhaust stroke. If the crank is off 180 degrees it will not fire up.
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was car just bought dead (no history shared)????
I did removed the distributor, OOPS, ;that wrecks, injector timing, !!
no IDEA me what EFI is there in poland, 91 YJ 4.0L i-6
ours, works like this....

CKP fires spark ever 120dgrees.
on our 90 4L the distrib. base locking clamp has a notch. that sets the timing correctly, unlike mine.

the CMP in the base of distributor is a sync pulse stator. (jeep named)
the FSM free factor service manual in the sticky post cover timing the distributor, unique to this engine it is.
page 8D-36 (service) to page 39
I will put a link to that page here. do the steps exactly as it tells you and , injection works, if the ICM is not bad. or CKP or CMP bad.

ICON 1990 first ICON is it. close enough.

one more warning per FSM it says removing the automatic transmission and putting it back wrecks the CKP or the tone holes there.
so step 1 is pull CKP before pulling any A/T box. CKP = crank pos. sensor.
CMP means cam sensor.
EFI = electronic fuel injected engines.

got this notch if yes,easy job, if not , sync;d it must be. per FSM. matching exact car, engine and market.

got this notch this really is question #1, beside did the car run before you pulled the dizzy./
timed at TDC #1 firing (both head valves closed) crank gear at 0degr.
then drop the dizzy , to the right tooth, per the FSM. and it will run now.
The oil pump slot must be pre-aligned. per the FSM

I must warn you some cars In Europe run different EFI , diffr. dizzy and PCm. not the same.
seen this my eyes. have friends in Spain and Italy. that are all different even same car, (seems like it is) but is not. ( due to smog laws each country yes)
the VIN not told , the first letters in the VIN tell the market it was sold to new. (and what parts are on the car)
or buying the wrong Dizzy off amazoned or fleabay for the wrong country. dang.
some cars in europe were even bought from USA and imported. (
nobody can guess any of this
on my jeep open hood
see brake booster, to the right of booster is large VIN tag 2x3 inches, shows a pile of codes there, this is how to buy parts based off that tag , only
or if engine swaps, way more hard work you get.
also some countries dictate where VIN tags go or what is on them. yes, complex on a world scale it is. sorry
Thanks guys for thr answers. The car came from Japan, and it was running before overhaul. This morning I thought I had it timed with exhaust TDC, but timing it with compression TDC did not changed anything. As before not even single fire. Wet plugs and fuel smell, and fuel in injestor rail. So, there is fuel, spark in the right timing, and nothing. Is there fuel injectiors timing required ?

Thanks again
Ok. solved.
What happened: I set the distributor so the rotor pointed at 4 o'clock for power TDC, like the fsm sdvised. The engine did not even fired once. So i decided to try to readjust distributor by one tooth each way. Second try she fired and worked beautifully. The rotor is at 5 o,clock rather than 4 - see the picture.
Thanks for the advices.


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so the cam chain timed wrong? ( seem at was all 100 % dismantled, ever inch to me so.........)
when we do any cam on any engine, we make sure the cam lobs work in a rational fashion. 4-cycle action. (hand turned at 19mm crank bolt , CW direction)

then do a WOT compression test. 150 to 180 psi, is expected, if not the cam was timed wrong.
we do all that even before valve cover is put back, (fuel pump relay removed so no fuel to burn TESTING)
i ALSO DO a TOP END OILING TEST before any valve cover put back, (FP relay still out)<<< just cranking it for 5sec, rest 1min crank, not to overload the starter.
to the rockers or HLA for sure.
last one I did , I made sure I had oil pressure cranking, again fuel relay out. (even to the point of hand gauge to removed sender port)
did you try a timing light to see that spark happens near the 0 mark in the crank pulley? cranked. dead. that be next in this list,
and lasts add fuel (the FP relay put back)
these steps avoid most new engine damage just after full engine assembly.
good luck.
btw fuel dribble at the rail proves NADA, only 41 psi cranking matters, not 10 , not but 41, but seems the compression will fail or the dizzy is all messed up.
or cam chain wrong and will make the dizzy fail too.
No DTC errors like CKP, or CMP> or others keyed on 3 times in 3 second span (jeep way)

this guy does it right here
he checks the HLA action as you turn the crank CW by hand

TDC #1 at top of cylinder, both valves, closed (HLA are both down) (this mark is the firing mark(at full compression running)

we turn the crank and see first do power stroke, then exhaust stoke and , then intake and last y stroke ever 180 degr. of the crank (4cylinders)
we call this validating it, the cam timing. The keyway key missing or wrong key? who knows if it fails this test what when wrong but you will find it as redone .

just for fun the MB SLk 232 super charger, 4banger ( I like how i thinks)$$$ on a budget.

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