Loud pop, hot car, rough drive (2 Viewers)

[17chee]

Hello everyone,

Newbie here, but I've been reading many of the posts on this forum and figured you all would be the right people for this question.

I've recently obtained a 1972 fj40 from a friend to watch over while he's out of the country for a few months. I was driving it down the highway when the engine started stuttering intermittently which eventually lead to a loud pop sound and more frequent stuttering. I got off the highway and noticed the water temp is now near 250 on the gauge. I slowly get the car home, I was less than a mile away. Driving slowly I didn't notice any stuttering.

Once I got home, I shut her down and popped the hood, boy was it hot. Most of the heat was on the driver side. I couldn't see any immediate signs of anything leaking.

Any ideas what caused the popping noise and over heating?

 

[brian]

sounds like a super lean carb issue

 

[73FJ40]

assuming an OEM setup carb and engine, Did the 3/4" hose attached to the tube below the front of the carburetor pop off? It allows a lot of air to bypass the carburetor, causing the engine to run lean, which causes the engine to run hot. The hose connects the PCV gave to engine vacuum.

 

[17chee]

Hey thanks for the quick replies! It is not the stock carb. Here's a picture of the engine bay from today after the issues started.

I did a quick search of some symptoms of a lean carb and that sounds right. The pop happened while I was coasting down hill in gear.

I'll check around the carburetor to see if anything came off.

 

[45Kevin]

The pop could have been a backfire?

Is the distributor loose? Timing issues?

 

[17chee]

I'm going to air on the side that it's not a timing issue. Before I got it, this car was his daily driver and he had no problems.

I'm hoping the pop was a backfire and not the head gasket.

How would I check if the distributor is lose?

 

[jembourbe]

How would I check if the distributor is lose?

Use your right and left hands to grab the distributor and wiggle it in various directions.

 

[17chee]

Use your right and left hands to grabgthe distributor and wiggle it in various directions.

Ah, who would have guessed it'd be so complicated

 

[45Kevin]

My experience is that backfires are a result of timing issues.
I'm not sure what would have caused the over heating. I am assuming you checked the coolant level.
Before you grab and twist the distributor, note where it sits now so if by some chance you rotate it you can at least get it back the position it is in now.

 

[4x4veteran]

Lose dizzy would cause timing change and temp rise but my first thought was play on the distributor shaft.
Looks stock so guessing points. Play in shaft causes point gap to change and misfire.
Never had an electronic go bad on me yet but I am sure the air gap discrepancy on the pick up could cause the same problem.

 

[Dizzy]

That Weber probably was never tuned properly. Fortunately, they are not difficult to tune.
Be careful not to lift the distributor from the oil pump which it drives.

 

[morganism]

put a socket on the exhaust manifold bolts, and see if they are still tight?

 

[17chee]

Alright guys, new development. I checked the distributor, it felt rock sold and in place. I checked the carburetor and noticed the top with the air filter felt loose, the whole top assembly slid off (The part attached to the black hoses with the "T" adapter in the middle). Is that supposed to happen? It was snug, but easy enough to slide off.

I kept exploring, took the radiator cap off and saw some weird brown crud in it. It looked like this:

I picked on it a little and it kinda felt like dirt, but I cleared most of it out. However, there doesn't seem to be any radiator fluid below the surface so I probably need to purge that then top it up.

Going further, I spun the car up and was checking everything under the hood, I noticed something dripping below the car... Smells like gas! I look on top of the car and see something in the lower front of the engine where the fuel comes in and it appears the bottom is leaking gas. What is it?

 

[Bripars40]

Alright guys, new development. I checked the distributor, it felt rock sold and in place. I checked the carburetor and noticed the top with the air filter felt loose, the whole top assembly slid off (The part attached to the black hoses with the "T" adapter in the middle). Is that supposed to happen? It was snug, but easy enough to slide off.

I kept exploring, took the radiator cap off and saw some weird brown crud in it. It looked like this:

I picked on it a little and it kinda felt like dirt, but I cleared most of it out. However, there doesn't seem to be any radiator fluid below the surface so I probably need to purge that then top it up.

Going further, I spun the car up and was checking everything under the hood, I noticed something dripping below the car... Smells like gas! I look on top of the car and see something in the lower front of the engine where the fuel comes in and it appears the bottom is leaking gas. What is it?

That’s the mechanical fuel pump. If it’s leaking check the hoses attached and if you do not see any cracks it’s probably time to replace the fuel pump.

 

[Dizzy]

I'd switch to an electric pump that has a more proven reputation for use with a Weber's specific float needle valve pressure. Leaking gas from the pump can go into the crankcase because the pump is driven by the camshaft. The pump's diaphragm might not be designed for ethanol blend; it doesn't look like an OE fuel pump. If it was leaking into the crankcase, you need an oil change.

The air cleaner assembly on a Weber is fastened to the air horn with screws, or nuts on studs, depending on your model.

It might be time to drain coolant from the block and radiator and do a proper flushing. You can test the thermostat with boiling water. I'd totally run an overflow reservoir because it would recover coolant purged from the radiator.

I'd like to the see the top, and accelerator linkage sides of your carb. Is there a vacuum hose from the carb to the distributor?

 

[hobbes]

What model of Weber has a site glass?

 

[rkymtnflyfisher]

What model of Weber has a site glass?

Looks like a little bit of a half breed carb. Bottom looks like an OEM but the top looks different.

 

[brian]

Yeah not a weber, probably oem.
Weber's are not known to run lean.

 

[17chee]

The carb might be OEM I leave it to your guy's expertise on this. I figured it wasn't because the top of it looked too new and a few things on this car has been upgraded (new gas tank, New electrical) but it is possible only the top is new. It does have a sight glass.

As for the fuel pump. How difficult is it to upgrade to an electrical fuel pump? Or since this is my buddy's car and he's not one to hold on to cars too long, should I just go the simpler mechanical route.

Dizzy, I'll get you some photos soon!

 

[Dodgrr]

dang, wish my friends would work on my car when I'm outta town.. Get to work, ya slackers!!