Fuel spitting out spark plug hole?!?

RaysnCayne · Sep 9, 2024

Hey y'all,
I was doing a compression check on my 87 305 TBI engine this evening and was getting fuel spitting out of the #8 spark plug hole while spinning the engine over to check pressures on the other cylinders.
Any idea why that'd be happening?? All the other cylinders were bone dry while I was doing my testing.
I unplugged the fuel pump relay (that's the one on the firewall, right?) so the FP wouldn't be running.

75gmck25 · Sep 9, 2024

If you have a problem with a rocker or pushrod on that cylinder, fuel may be accumulating and not getting burned. It’s amazing how smooth a stock 350 can be even when one cylinder is not contributing.

If you have the time, I would pull that valve cover, leave the fuel pump off, and watch the valve train while someone else cranks the engine.

RaysnCayne · Sep 9, 2024

It runs really smooth. It sure sounds like it's firing on all cylinders.
But she GUZZLES gas like nobody's business - way more than a little (mostly stock) 305TBI should. So I need to figure out why. So I'll act on your suggestion and see if I see something there.

legopnuematic · Sep 9, 2024

Being a TBI, stuck/sticking injector perhaps?

RaysnCayne · Sep 9, 2024

Maybe?
But since this isn't port/individual injectors, I'd think I'd be getting fuel out of more than just one cylinder on that bank if that was the issue.
(I gasket-rebuilt the TBI about 4 months ago. Seemed to be doing its thing just fine afterwards.)

legopnuematic · Sep 9, 2024

Maybe maybe not, when the engine shuts off there will be at least one intake valve open in some capacity (with overlap there will be another slightly open), if it’s flooding the intake it will flow into the cylinder with an open intake valve.

RaysnCayne · Sep 11, 2024

75gmck25 said:
If you have the time, I would pull that valve cover, leave the fuel pump off, and watch the valve train while someone else cranks the engine.

I pulled the valve cover and everything looked hunky-dory underneath. I checked the rockers and they all seemed fine. Nothing looked to be out of adjustment. I watched as my wife turned it over and everything seemed to be functioning just fine.

For this test, I unplugged the injector pods. There was zero fuel spitting out of #8, but I did notice some wetness that smelled like gas on the manifold by the #7 hole. But after turning it over a couple more times, I didn't see any fuel coming out of #7.

So IDK, out of sheer ignorance, I'm chalking random fuel spitting out of the two rearmost cylinders up to a TBI phenomenon that happens when you do tests like this.

Rusty Nail · Sep 11, 2024

Ya .
You'll have to change the intake gasket or do ya reckon the head is cracked between 6 and 8...?? head gasket mebbe.

Im goin with cracked cylinder head - final answer.

xc_hide_links_from_guests_guests_error_hide_media

RaysnCayne · Sep 16, 2024

There's some serious merit to the cracked head (or blown head gasket) idea. The plugs look a bit yellow/orangey. And I do lose a little bit of coolant over the course of a couple months. It's just that the liquid being spat out during this exercise was gas and not coolant.

This 305 would probably keep on truckin' another 3-4-5 years in this state. But I'm hoping to build a 5.7 TBI to replace it in the next year-ish. So I guess I'll just put it all back together and ignore these signs of danger.

Fuel spitting out spark plug hole?!?

RaysnCayne

Member

75gmck25

Full Access Member

RaysnCayne

Member

legopnuematic

Licensed Junk Dealer

RaysnCayne

Member

legopnuematic

Licensed Junk Dealer

RaysnCayne

Member

Rusty Nail

Full Access Member

RaysnCayne

Member

Similar threads

Latest posts

Forum statistics