Last try for leaking mechanical fuel pump

[johnnyzoom]

Hey everybody-

A couple months ago you guys helped me with a leaky fuel pump. Embarassingly enough I thought it was leaking fuel, 3 pumps later I realized it was leaking oil where it mounts to the engine (200 i6, 64 Merc Comet, automatic).

Addo talked me through tapping the block and trying shorter bolts that wouldn't bottom out, but it always starts dripping oil within a few days, averaging about a quart every 2 weeks, from the bottom of where it meets the block, nowhere else.

I've tried every idea I could find or hatch up myself (different fuel pumps incase one was warped, different gasket material, two gaskets, no gasket, different gasket sealers, etc) and I just can't get this thing to seal. Best guess is that the bottom of the engine block where the pump bolts on may be warped, although there's no visible damage.

I could go to electric, but fear I'd have the same problem with sealing that part of the block (I think there's info on the forum somewhere about a Chevy bolt-on plate that fits the six when switching to electric and losing the mechanical). If there's a chance it'd be more likely to seal wthout the weight and the cam stroking the pump, I guess I'd try it. Should I pay somebody to weld it shut? Or 'braize' it myself?

The pump delivers fuel perfectly so far as driving goes.. Sorry about the longwinded question, hope I've explained clearly.

Thanks a lot-

Johnny

 

[Lazy JW]

Pull the fuel pump and clean the mounting surface of the block super clean. Get a strong light in there and check for a crack. If that looks good then get a short, accurate straight-edge and check for flatness. Let us know what you find there. I like Permatex Aviation (the goopy, gunky, sticky stuff) gasket sealer for this type application.
Joe

 

[johnnyzoom]

Thanks for the advice. Haven't had time to analyze the pump and the block as you recommend, but will asap. In meantime tried some of the sealant, it appears to be slow drying, any idea how long to wait before running after applying?

The only thing I can trace back is that I may have been a little rough getting the old pump off, it was stuck on pretty good (bolts came out easy, but the gasket was tough). I'd think the bulletproof six would take what I gave it, let's hope so.

Will report findings very soon.

Thanks

 

[Mercury Mike]

You don't have to wait for it to dry. It's a sealant, and it holds pressure. It turns rubbery. If you used enough of it (even though I never like using it engine side, I always use it parts side to hold the gasket in, but you have to use it block side this time), you should be alright. But yeah, check for straightness.

 

[johnnyzoom]

Sorry about lapse on this, weather has prohibited me from getting under the hood 'til today.

Followed suggestions with good light, mirror, and straight edge. Can't detect any problems in the block, used a couple different sized levels to check straightness in all directions where it mounts. Also checked the fuel pump(s) same way. I've crawled under the car after running to watch the leak and make sure it was coming from that spot. Last idea for inspection is to get digital camera back from friend and try to get that in there on hi-rez for some close-ups.

Having trouble thinking of what I'm missing. Obviously something is keeping it from sealing up. Observed pump at idle and engine doesn't appear to shake much at all, it's pretty smooth. I can get away with a short trip with almost no leaking, the longer I drive and the hotter the car gets the more of a leak I get, probably to be expected.

Could something as simple as throwing an extra washer on the bolt help? I've actually tried with and without the washer, no difference.

Purchased different style fuel pump I wanted to try, doesn't have the filter on top (already have extra inline before pump), wanted to see if it might mount better.

I'd feel like a loser getting it welded shut and going electric, I'm hoping you guys might have a couple tricks left up your sleeves.

Thanks a lot

 

[Lazy JW]

Ok, the block is good. With no fuel pump in the way, carefully thread the bolts all the way in the holes. Hold the fuel pump up beside them to see if the bolts are too long to tighten the fuel pump all the way down. There could be crud in the holes preventing the bolts from going all the way.

Also, with no bolts or gaskets, hold the fuel pump in place to see if you can manually push the fuel pump up tight against the block. It needs to be able to sit right smack tight on the block with no gasket. If not, you have the wrong pump or the wrong arm on the pump.

Joe

 

[johnnyzoom]

Tested as recomended above, they appear to be fine (went to a slightly shorter bolt last time around to help with this).

Today was one of those days: snapped head of bolt flush with engine block, 2nd time in a couple months! Probably just coming up on torque spec. Last time was able to remove and tap, this time I dunno. Barely any clearance to get a drill in there, even with right angle attachment. Tried helicoil set, still need to drill a lot more to go that route. Wonder if it's worth the continued punishment to the engine block with the sloppy drilling to pursue this?


Thanks for your patience- Johnny

 

[Lazy JW]

Bummer. Try using a small cold chisel and a light hammer to remove the broken bolt. Use the corner of the chisel, tap it straight in to get a notch, then tap with very light blows to turn the bolt out.

I'm wondering if the bolt hole is drilled too deep and oil is leaking around the threads. A good coating of thread sealer should cure that problem.
Joe

 

[johnnyzoom]

Thought I'd post the resolution to this for what it's worth.

-Let car sit for a day without running to let cool off completely and dry oil residue.

-Switched to '72 200 style fuel pump (no filter on top, seems to meet block tighter), then threw JB weld all over the offending section of pump and block.

-Let dry for a week while out of town.

Hate the cheesey temp fix, but so far it's worked. Will probably seal up and go electric when/if this fails.

Thanks for the suggestions and help.