90 Comanche 4.0 fuel smell

[russel730]

1 hour ago, 88towmanche said:

 

If you're smelling fuel with the truck sitting static overnight probably not manifold related.

 

Tank gasket leaking is my bet - mine leaks at the top 1/3 of the gasket - if I fill the tank it stinks like hell until it gets down to 3/4 tank.  

I had the exact same issue with mine when I bought it. Unfortunately, it wasn't the gasket. The brazing around the fuel lines from the sending unit like to crack ever so imperceptibly and leak when you fill the tank up.

[88towmanche]

19 minutes ago, russel730 said:

I had the exact same issue with mine when I bought it. Unfortunately, it wasn't the gasket. The brazing around the fuel lines from the sending unit like to crack ever so imperceptibly and leak when you fill the tank up.

 

Man I hope that is not the issue with mine (sounds like a hassle) - my truck sat for like a decade before I bought it, PO would fire it up every 3 or 4 months but never used it or put much gas in it so my theory is the top of the gasket just dried out - you can see where it's leaking if you fill up all the way - at least that's what I thought....now going to take a closer look at those hard lines.

[russel730]

4 hours ago, 88towmanche said:

sounds like a hassle

Nah, Just have to replace the sending unit which isn't too much more effort than replacing the gasket.

[OldManComanche]

Have you tried to start it and just let it run for a minute? I had the rubber hose coming off of the fuel pump leak from a crack in the hose. It would leak a drop of gas about every 30 seconds. it would drip directly from the hose to the ground, so no damp area around the fuel pump. when you shut the engine off it would stop leaking. I normally park it on the gravel drive and didn't notice a drip spot till I had it running for a few minutes on concrete.

 

If It was EASY, everyone could drive a Jeep!

[comanche32]

Well finally had a chance to spray carb cleaner on the manifold. It stumbles quite a bit when sprayed on the manifold a little above the 02 sensor. I'm wondering if it's cracked and I can't see it.

[cruiser54]

Most likely. What about on the intake manifold?

[comanche32]

I sprayed the very front bolt and it stumbled also. It never did die just affected the idle some.

[cruiser54]

It has a leaking intake manifold then. How about the rest of the intake manifold? Have you sprayed it?

[comanche32]

The best I could there's alot of crap in the way. I may try again today why would it stumble when I sprayed the pipe above the 02 sensor

[cruiser54]

Likely because the oxygen sensor got some carb cleaner on it. 

[comanche32]

Well I sprayed the manifold the best I could again today. It bogs down when I spray to the bolt that's missing. But that's right above the o2 sensor. I'm wondering if it's only bogging down because its getting on the o2 sensor. Would a intake gasket or cracked intake cause the random bucking issue I'm having at 45 to 55.

[comanche32]

Another thing I noticed today while I was spraying carb cleaner. If I manually hit the throttle I can hear air sucking in. I looked for a vacuum leak everywhere. It seems like it was coming from around the throttle body. But all the vacuum lines were intact. I could really hear it when would bump the throttle instead of even pressure 

[Classy Comanche]

Wait. Does it whistle? Or make any sound other than the "suck" sound like air intake?

[comanche32]

Yes sounds like air intake a low whistle 

[Classy Comanche]

The guy that works on my truck said my truck started making a whistle sound when warm/hot and he looked into it while I was having somthing else done. And I quote "Several people chimed in about possible loose intake manifold bolts. I sprayed some brake cleaner in that area and sure enough, a leak at the manifold to cylinder head surface. Both guys said they just tightened the bolts and they were fine again, going on two years for one of the guys. I checked yours, and found a few loose, tightened them, and no more leak or noise. Idle has also been better." Maybe that is it? He said that silenced the whistle immediately 

[cruiser54]

This^^^ has been my experience. 

[comanche32]

Well since one is missing I'm guessing that's where the problem is. I drove it to work today and it did fine for about 25 min. Then it started doing the bucking at 45 to 55. One of these days il take the manifold off and replace the gasket and bolts when I get time 

[cruiser54]

why not replace the bolt with washer and tighten up all the other bolts? Half hour job. 

[comanche32]

Yes I will try that first I've tightened all of them except the one that's missing.

[comanche32]

The very back bolt on the rear bottom of the manifold does anyone know if that was a bolt or stud from the factory 

[comanche32]

I found a diagram of a renix 4.0 if its right then the Last bottom is a stud not a bolt. If that's the case then it's not missing its broke off. That's just fantastic I'm betting there's no way to drill that. 

[rokinn]

Yes it is indeed a stud.  If you reread my post from earlier in this thread I stated what I had to do to solve the problem.  I have read of one person on CC who was able to remove the broken stud by drilling and using an easy out but you have to remove the manifold even then.  You will need a right angle drill adapter and a cobalt bit.  Preferably a short one.  Perhaps only.  You can get one on amazon.  But that will only work if the stud is not too rusted to the head.  Otherwise plan on pulling the head.  My only performance issue was a high idle but it was only a matter of time before other problems reared their ugly head.

[comanche32]

I knew it wouldn't be as easy as a missing bolt. That's how my luck goes