Blowing Fuel Pump Mounting Gaskets

[rick3216]

Hoping someone can help me figure out why my M37 with stock 230 engine is blowing fuel pump-to-block gaskets. I rebuilt the pump due to gasoline leaking out of pump and onto engine block. Now, after running engine for 10 minutes I hear a whistling noise which is air blowing out past a newly created tear in the gasket. I have replaced the gasket and coated it with form-a-gasket but same thing happened. I then questioned the PCV so I disassembled and cleaned the whole fording valve assembly and inspected the PCV. When held in its vertical position it will not allow air to pass into the crankcase but allows air to pass from crankcase to carb elbow - seems normal. I also removed and inspected the oil filler-to-carb elbow vent tube and it is clear. I have noticed the engine missing just a little while idling which it did not do before. Not sure if it is related to my problem.

Cannot figure out why I am blowing the fuel pump-to-block gaskets. Compression test is low to high 90 psi so I don't think it is excessive blow by. Please send suggestions? Thicker gasket material?

[w30bob]

Hi Rick,

You mentioned checking the PCV and fording valve, but did you check the pipe that exits the block that connects to the fording valve? How did you check that it's unobstructed?
Just thinking out loud here.

regards,
bob

[rick3216]

Hi Bob,

I removed the pipe in question when I removed the fording valve assembly. It all looked very good. Both fording valves (from block and from oil fill pipe) are open. When I run the engine and close the fording valve going to the crankcase it quiets the engine but does not effect idle speed. When I close the fording valve from the oil fill pipe it causes the engine to run rough. Even if a ring got stuck or broke I would think the crankcase should have two good ways to vent. To actually have the leaking gasket whistling seems very odd. I need to get the tools to do a leak down test.

I did an oil change 2 months ago after one year and about 150 miles and the oil was very dark in color which I did not expect to see.

Although I my mating surfaces for the fuel pump and block were spotlessly clean I may need thicker gasket material.

[w30bob]

Hi Rick,

Yeah, something is amiss. To blow thru a gasket between two flat mating surfaces takes quite a bit of pressure............and there shouldn't be much pressure. Having the PCV plumbed into the intake causes a suction on the PCV.......so any positive pressure in the crankcase is trying to tell you something. I'd stick an air hose in the oil fill tube with a rag wrapped around the hose to cover the rest of the opening and put a couple psi (don't go crazy) in the crankcase. See if air comes out the PCV when the valve is open. It should want to come out the PCV way easier than blowing thru a gasket. If it comes out the PCV then you've got a ring problem, meaning you just making way too much compressed air to flow thru the PCV in between strokes.......if not something is blocking the PCV air path.

regards,
bob

[just me]

I would expect high crankcase pressures would play havoc with your other seals. Oil should be pouring out the rear main if there is enough pressure to blow a gasket. Remember, that when the fording system is active, it IS pressurizing the block in order to prevent water entry. You should not be running the engine with it engaged. On our M38 we set the fording valves up to maintain a very small low pressure (2"hg or so) in the crankcase to prevent oil leaks as well as possible. I will do the same to the M37 once the new T245 is rebuilt and installed.

[MSeriesRebuild]

Hoping someone can help me figure out why my M37 with stock 230 engine is blowing fuel pump-to-block gaskets. I rebuilt the pump due to gasoline leaking out of pump and onto engine block. Now, after running engine for 10 minutes I hear a whistling noise which is air blowing out past a newly created tear in the gasket. I have replaced the gasket and coated it with form-a-gasket but same thing happened. I then questioned the PCV so I disassembled and cleaned the whole fording valve assembly and inspected the PCV. When held in its vertical position it will not allow air to pass into the crankcase but allows air to pass from crankcase to carb elbow - seems normal. I also removed and inspected the oil filler-to-carb elbow vent tube and it is clear. I have noticed the engine missing just a little while idling which it did not do before. Not sure if it is related to my problem.

Cannot figure out why I am blowing the fuel pump-to-block gaskets. Compression test is low to high 90 psi so I don't think it is excessive blow by. Please send suggestions? Thicker gasket material?

Numerous issues can cause higher than normal pressure in the crankcase, however a couple of other issues quickly come to mind when I read your problem description. #1, 90 PSI compression readings are extremely low and that is very likely to be the cause of the skip you are hearing at idle. Obviously you have either some valve issues in play or ring/cylinder wall wear that is in the excessive category; most likely it will be the latter based on the info you have offered in your post. If that is the case and ring/cylinder wall wear is the cause of low readings, there is only one fix, it's engine rebuild time. A simple follow up compression test will either show up clearly or eliminate valves being the problem. #2, In relation to the consistent gasket failures, I would clean up the areas really well and search for a crack in the engine block boss or the fuel pump mounting flange, not very likely you will find a crack, but it's worth a close look. It is also very common to find gasket flanges that are no longer flat as a result of years of repeated heating and cooling. This means the two surfaces being no longer flat, are not mating evenly. With gaps between mating surfaces, a gasket can not compress tight enough to keep it from blowing out in the area of the gap where there is no support for the gasket. If there is no cracking found, the flange surface can easily be trued on a precision surface grinder while the pump is disassembled, after which a new gasket will hold just fine. This is the problem cause of many seeps on older engines, and the low compression readings you spoke about is causing internal blow by in a huge way because the engine as original in a M37 has no external atmospheric venting where blow by can easily be detected from outside. It's there, you just don't see it. If I were you, I would approach it this way. First verify the reason for the low compression, I highly suspect a rebuild is knocking on your door. While the engine is disassembled, check out probable causes for this gasket failure and correct it during the build. We check and resurface every flange on every component while an engine is down, it will insure no oil leaks and other issues like having to run your engine with the choke partially pulled out because of vacuum leaks. It is very common for these vacuum leaks to be caused by gasket surfaces that are no longer flat, thus making good gasket sealing impossible.