Guest ssherrick Posted March 17, 2017 Share Posted March 17, 2017 When I last drove my 1939 Model 41 last fall, the engine died twice when I got up to cruising speed. After setting for a few minutes, the engine started and ran fine until I was at cruise speed and then quit running again. AAA brought me home and due to a series of issues, I am just now starting to try to find what the issue may be. I did a compression check and all cylinders were 60 to 65 psi. I also noticed that there is an extreme vacuum leak at the wiper motor. Could a large vacuum leak cause an engine to shut down at cruising speed? If not, what might be some consequences of a large leak? What sequence of steps should I take to determine the cause of the engine shutdown? I definitely appreciate any help and advice anyone may have for me. Link to comment Share on other sites More sharing options...
JFranklin Posted March 17, 2017 Share Posted March 17, 2017 A vacuum leak would affect carburation and mix Link to comment Share on other sites More sharing options...
pont35cpe Posted March 17, 2017 Share Posted March 17, 2017 The way you describe it quitting when you reach cruising speed sounds like it`s starving for gas. Does it have an inline fuel filter? It could be getting stopped up and restricting the flow, runs fine at low speeds and dies at cruising speed. I don`t think the vac. leak is your problem. I`d check the fuel line from the tank to the carb., any old rubber hoses/ fuel filter/ fuel pump. 2 Link to comment Share on other sites More sharing options...
carbking Posted March 17, 2017 Share Posted March 17, 2017 Check the vent on the fuel tank. Many older vehicles were vented through the gas cap. Newer caps do not have the vent. If the tank is not vented, at some point, the tank will become locked by vacuum, and fuel will not flow from the tank. Allowing it to sit for awhile will allow the pressure (vacuum in this case) to equalize, and the engine will again run for awhile. Another possibility would be fuel filter, although a partially clogged filter will not normally cause the engine to stall; rather it will run very roughly unless the RPM is reduced. Jon. 2 Link to comment Share on other sites More sharing options...
Guest ssherrick Posted March 18, 2017 Share Posted March 18, 2017 I am pretty sure that this car doesn't have an inline fuel filter but does have the filter inside the inverted fuel pump bowl. I haven't taken the fuel pump bowl off yet. Will be doing that this weekend. I don't know the history of this fuel pump. I have tried to get information from the previous owner to determine if it had ever been rebuilt but am not getting any response. I think I will order a rebuild kit and do it anyway. I also have to troubleshoot the gas gauge. It barely moves up when I start the car. I don't know if it's a wiring issue, gauge issue or bad sending unit. I am currently using a method I learned in the fifties to measure gas by inserting a section of hose into the tank and seeing how many inches are wet when I pull it out. That attests to my backwoods upbringing. It seemed that none of my Dad's old cars had working gas gauges. Link to comment Share on other sites More sharing options...
Terry Stock Posted March 18, 2017 Share Posted March 18, 2017 Strange. Message #4 is the same as one I heard during the week from a 1950s Rover owner. The seal had deteriorated and swollen and it somehow became airtight. Do check the gas cap. Link to comment Share on other sites More sharing options...
Grimy Posted March 18, 2017 Share Posted March 18, 2017 I agree with the gas tank / gas cap vent especially. Suggest you trace the fuel line from the tank to the mechanical pump. If there is any flexible hose, including the factory flex hose entering the fuel pump, such hose could be partially collapsed on the inside, especially under the high suction provided by the pump at cruising speed. Such hoses fail from the inside out. I'm also a bit concerned about the 60-65 psi compression pressure, which seems low by one-third. I just checked my MoToR Manual, which specifies 125 psi at 1,000 rpm. I've never tried to test one cylinder at a time at a high idle. Rather, at cranking speed, I use compression ratio (yours is 6.15) x ambient pressure (14.7 psi at sea level, dropping with altitude). At cranking speed, you should optimally be getting about 90 psi at or near sea level Of course, if you did the compression test before capping off the vacuum line to the wiper, I think should you should run the test again, and I'll bet you have better results. If the fuel pump hasn't been rebuilt with anti-ethanol material within the last 6-7 years, I'd rebuild the pump on General Principles. Best wishes, and please keep us posted on what you find. Link to comment Share on other sites More sharing options...
Guest ssherrick Posted March 18, 2017 Share Posted March 18, 2017 Thanks for the advice on the gas cap and fuel pump. The cap is a new generic cap from NAPA. I will loosen it to see if that makes a difference. When I got the car the cap was missing. I think I will rebuild the fuel pump just out of principle. Will do another compression check with the wiper vacuum line clamped off to see if there is any change. Link to comment Share on other sites More sharing options...
Guest ssherrick Posted March 18, 2017 Share Posted March 18, 2017 Another question concerning the fuel pump - can a pump from a 1938 or 1940 248 be put on a 1939? I understand that the inverted fuel pump was a one year feature. It just doesn't seem right to have the bowl pointing up. Plus it is extremely messy removing the bowl for cleaning. Link to comment Share on other sites More sharing options...
Grimy Posted March 18, 2017 Share Posted March 18, 2017 The "inverted" pump (bowl on top, upside down, was a 1943-and-later service replacement item for Cadillac to address vapor lock issues encountered with the factory upright pump used 1937-42; I don't know whether Buick did likewise. Yes, it's messy to check but infrequently done. Paper or plastic cup is helpful to catch more than half of the dumped fuel, and old towels underneath are useful. Regarding the factory flexible hose entering the pump, take your old one in to a place like Hoses Unlimited and they'll make one up for you out of braided stainless within a day--while you wait, if you're lucky. But then you need to fake the original lacquered cloth-over-rubber sure-to-die-soon hose. I've taped off the fittings on both ends, sprayed on about six coats of rattle can paint, then while the last coat is still tacky, touched it with a red shop towel to replicate the textured appearance of the original. Link to comment Share on other sites More sharing options...
pont35cpe Posted March 18, 2017 Share Posted March 18, 2017 I`m having a hard time understanding how an inverted sediment bowl would even work.. Wouldn`t all the trash and moisture that settles in the bottom of a normally upright bowl settle to the bottom of the inverted one and all the trash be sucked right on thru, defeating the purpose of a sediment bowl? Or does the inverted bowl have an elevated outlet stem that draws the fuel from the top of the inverted bowl, therefore above the trash/moisture that would settle to the bottom? Link to comment Share on other sites More sharing options...
Grimy Posted March 18, 2017 Share Posted March 18, 2017 Good morning, pont35cpe, your interesting question sent me back to my trusty 1935-46 MoToR Manual that I bought in a thrift store for 25 cents in 1962. The inverted pump is a Type AA by AC fuel pumps. The diagram shows a vertically mounted almost cylindrical strainer within the bowl, so apparently fuel is pumped into the bowl and through the strainer into the line serving the carb. The narrative doesn't explain even that, Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now