Weird noises (with video)... still...

[JayTheGent]

Hey all,

 

Still having the weird noise occasionally on hot starts...

 

Here's a link to a youtube video showing what I'm talking about:

 

Please let me know if you have any ideas... possible culprits that I could think of are:

-out of time... again (I'll check tonight)

-starter

-distributor... again

-temp sensor

[Slartibartfast]

Huh. It's like the starter is hitting much higher compression on one cylinder. And then it starts up fine.

 

Any loss of coolant, oil consumption, horrible fuel mileage, codes? I'm wondering if something is leaking into one of the cylinders, raising compression like a hydrolock, and being blown out when the engine starts.

[Rebelord]

Huh. It's like the starter is hitting much higher compression on one cylinder. And then it starts up fine.

 

Any loss of coolant, oil consumption, horrible fuel mileage, codes? I'm wondering if something is leaking into one of the cylinders, raising compression like a hydrolock, and being blown out when the engine starts.

That would make sense if one of his injectors is leaking. Which could cause a odd cold/hot start like issue. *Thumbs up*

Edited May 21, 2016 by Rebelord

[JayTheGent]

Hey guys, thanks for responding! Sorry it took me a few days to get back to you.

 

Huh. It's like the starter is hitting much higher compression on one cylinder. And then it starts up fine.

 

Any loss of coolant, oil consumption, horrible fuel mileage, codes? I'm wondering if something is leaking into one of the cylinders, raising compression like a hydrolock, and being blown out when the engine starts.

Slight loss of coolant due to a crack in my radiator. Patched it temporarily until I can hit the scrap yard and pull another. No oil consumption, I change the oil like clockwork and I have been short. Fuel mileage is right around 16 mpg, which is where it has been since I bought it. It is strange that it only happens on hot starts. I have driven until hot, turned it off and immediately tried to start it and she fires right up. But.... if I let it sit for more than 10 minutes or so, it has the problem. Also, this video didn't show the whole process, I tried cranking 2 or 3 times before I started recording. I think you are on the right track, because when it does fire up, I smell a huge impulse of exhaust... that made me think there was too much fuel being dumped in.

 

 

That would make sense if one of his injectors is leaking. Which could cause a odd cold/hot start like issue. *Thumbs up*

 

If it is a leaky injector, how do I check this? If the motor was cold, I could pull the plugs and check for wet ones, but because the issue only occurs when it is hot, I would imagine that by the time I checked all plugs, the fuel would evaporate. Could I slightly advance the timing to maybe 10 degrees btdc? This would get the plugs firing a little faster, not letting them get over saturated?

 

On that note, could it potentially be the fuel pressure regulator? To check the vacuum line, is it recommended to pull off the intake plenum? It looks like a pretty tight fit back there.

 

Thanks again for all the help!

[Slartibartfast]

Interesting. Yeah, my guess then would be that you've got a small injector leak. The fuel rail is still pressurized when the truck sits, so a small leak would mean that over time that fuel makes its way into that cylinder. On a hot start, it wouldn't have time to leak much; on a cold start, the fuel would drain past the rings into the sump. How's your oil look? Any gas smell? You don't want gas thinning out your oil, that happened to my cousin's Spitfire (mechanical fuel pump diaphragm failed) and by the time she figured out why the oil level was so high, the bearings were toast.

 

You could pull out the injector rails, turn on the ignition so the pump pressurizes the system, then see if one or more injectors are piddling. That means taking the intake apart but it would give you a pretty good idea of what's going on. You might be able to get some idea from pulling the plugs and looking for a rich one, on the off chance the leak is fast enough to make it run rich once the engine's running, but if it is a leaking injector you'll likely have to dig in to get them out anyway.

 

You might also try sticking a boreoscope camera down the spark plug holes. I got a cheap USB one for $20 off Amazon. That might help you see which cylinder has fuel puddled in it, though you'll want to crank the motor over a couple times before checking, as the fuel may be puddled behind the intake valve instead if the engine stops with that particular valve closed.

[JayTheGent]

You guys are rock solid at this stuff! Had the issue again today and quickly started pulling plugs. I'd pull a plug, check for fuel, reinstall and repeat. Plug 3 was soaked in gasoline, the rest were bone dry. Swapped the plug for a dry one and she fired right up.

 

Luckily the injector for plug three is exposed. Next step is to do what you recommended. I'm basically going to remove the injector and prime the pump to see if there is a leak.

 

I will keep you posted!

[JayTheGent]

Interesting. Yeah, my guess then would be that you've got a small injector leak. The fuel rail is still pressurized when the truck sits, so a small leak would mean that over time that fuel makes its way into that cylinder. On a hot start, it wouldn't have time to leak much; on a cold start, the fuel would drain past the rings into the sump. How's your oil look? Any gas smell? You don't want gas thinning out your oil, that happened to my cousin's Spitfire (mechanical fuel pump diaphragm failed) and by the time she figured out why the oil level was so high, the bearings were toast.

 

You could pull out the injector rails, turn on the ignition so the pump pressurizes the system, then see if one or more injectors are piddling. That means taking the intake apart but it would give you a pretty good idea of what's going on. You might be able to get some idea from pulling the plugs and looking for a rich one, on the off chance the leak is fast enough to make it run rich once the engine's running, but if it is a leaking injector you'll likely have to dig in to get them out anyway.

 

You might also try sticking a boreoscope camera down the spark plug holes. I got a cheap USB one for $20 off Amazon. That might help you see which cylinder has fuel puddled in it, though you'll want to crank the motor over a couple times before checking, as the fuel may be puddled behind the intake valve instead if the engine stops with that particular valve closed.

So it wasn't quite as easy as I'd hoped. Ended up having to pull the intake plenum off to get to the leaky injector off. The heads of the screws holding the injectors in stripped so I had to "extract" them.

 

Ordered a new injector, intake manifold gasket and valve cover gaskets (figured I'd kill two birds since the manifold is already off).

 

Started thinking about doing the head gasket and crankshaft seal while I've gone this far. I replaced the timing belt a while back but couldn't afford a new tensioner. I was thinking that if I did the tensioner on Friday, I could unbolt the exhaust and pull the heads too.

 

With nearly 215k on the motor, I'd hate to put the manifold back on and do the tensioner, then have the gasket give out in 15k when I could have spent the extra hours to avoid it...

[adamzan]

This is not one of those vehicles where the head gaskets just "go". It would take multiple severe overheats or running for years with water or never changing the coolant. They have 5 head bolts per cylinder!

[Slartibartfast]

When I did the TB on my '93 I ended up taking the manifold off and cleaning out under it. There was a lot of rat crap under there and I was a bit worried that I'd drop something crunchy into the cylinders when I replaced the plugs if I didn't give it a good cleaning first. One tip, don't get the crap stamped-steel Victor Reinz gaskets for the intake. I did and they were useless. Too thin so nothing lined up properly, and with the pitting on the heads, there was no way they'd hold coolant for long. I tore that crap back out and got a Fel-Pro set that fit perfectly.

Good call on the valve cover gaskets, but yeah, the head gaskets are not a common weak point on these.

[JayTheGent]

When I did the TB on my '93 I ended up taking the manifold off and cleaning out under it. There was a lot of rat crap under there and I was a bit worried that I'd drop something crunchy into the cylinders when I replaced the plugs if I didn't give it a good cleaning first. One tip, don't get the crap stamped-steel Victor Reinz gaskets for the intake. I did and they were useless. Too thin so nothing lined up properly, and with the pitting on the heads, there was no way they'd hold coolant for long. I tore that crap back out and got a Fel-Pro set that fit perfectly.

 

Good call on the valve cover gaskets, but yeah, the head gaskets are not a common weak point on these.

Hahaha I've heard of that happening! I try to stick with Fel-Pro for all of my gasket! Used a little bit of red silicon and it went on like a champ.

 

I decided to just do the following:

-new intake manifold gasket (upper)

-new fuel injector

-new valve cover gaskets

 

50 bucks (thanks amazon prime) and two hours later, she seems to be running great. I went on a bunch of quick trips since that's usually when the symptoms show and she fired right up every time.

 

Also cleaned out quite a bit of mud from the engine bay! Crazy how much junk gets under there.

 

I'll give her another week before I say it's completely solved, but I'm pretty sure that was the problem. Thanks a bunch for all the help guys!

 

One thing I have noticed is that I'm about 100 RPMs higher at idle, I think I'm going to adjust the throttle position sensor in the morning to drop back down to 750.

[JayTheGent]

It was not the fuel injector. I did have a leaking fuel injector which was the cause of the popping sound, but the not start issue still remained.

 

It was... drum roll... the distributor... the same distributor I have replaced twice. I will be doing a listing about it... It is the Duralast (AutoZone branded) one.