So I got the 39 straight 8 running today after fixing some electrical issues but I have an odd problem with the carb. It is a rebuilt one barrel carb with a 6 volt electric fuel pump supplying the gas. When I turn the key on the pump starts running but never seems to quit, just a steady pumping. I remember when electric pumps would slow down once fuel was pushed into the carb, maybe today's pumps are different. Anyway, that is not my problem. Every time I start the car I have to squirt some gas down the carb throat. I can run the motor for 10 minutes, shut it off, try to restart it and it won't fire until I squirt a shot of gas into the carb. When it does run, it responds quickly when I give it gas. It lopes a little at idle but never dies. Any ideas what I should look for? And, as always, thanks for any and all help.
Thanks for the reply. I don't know a whole lot about carburetors but wouldn't a bad accelerator pump cause the motor to stumble when it is running and you give it more gas? Once my motor starts it responds smoothly and accelerates without hesitation.
[Where is pump mounted? Should be as close as possible to the tank and below fuel level is possible. The pump might also be sucking air on the suction side due to hole or crack in line. Sounds like its getting just enough fuel to run. Can you drive it or or just idling? Was the mechanical pump on the motor left hooked up? If that is the case the electric pump may be bad.
The 5 gallon can sits in the passenger floorboard and the pump is mounted just below it on the frame. Can is almost full and all fittings are tight. Once cranked the motor runs and accelerates smoothly without any hesitation. I have driven it around my backyard a couple times without any problems. The mechanical pump is not hooked up.
I thought I found my problem. There was a wasp stuck in the inlet on the fuel pump! When I removed it the pump flow improved a lot. But, while looking down into the throat of the carb and moving the throttle linkage there was barely a dribble of gas. Since I don't know how long ago this carb was rebuilt I am going to have it rebuilt again. I guess I'll get the bugs worked out of it sooner or later!
Anybody want to buy an 800 pound boat anchor? I did a compression test today and it wasn't good. #1 35PSI #2 70PSI #3 80PSI #4 55PSI #5 75PSI #6 55PSI #7 55PSI #8 70PSI I don't suppose there is any chance that adjusting the valves might help. When I pilled the plugs they were all black and smelled slightly of gas. Also, the plug gap was wrong. It should be .025 but they were all .035 so I reset them. When the motor runs it does smoke a little but I thought that was just from the oil and Stabil spray fog that I put in the cylinders to help free up the motor.
Good story about the hornet! If you hear hoofbeats you don't look around for a herd of zebras. If this motor has sat as long as it sounds like, the rings might be set up. You can try a soak in ATF to see if they will free up. I had a similar problem with an OT tractor I did a valve job on. When I had the head off it looked good, no ridge at top of cylinder, good crosshatch pattern but had low compression on on all 4 holes. Did a wet check ( squirted oil in cylinders and checked comp) and it came up a bit. I'm not a big believer in additives but I've had good luck with a product called Sea Foam. You can find it in most parts stores and a lot of discounters now. I was one of the first retailers to sell it in my NAPA store. I took a can and poured it down the carb throat with engine running and held the idle high enough to keep running until I had about 1/3 of a can in it, let it quit and sit for an hour. I went back and started it, then ran the rest of the can through.(warning, it'll smoke like Cheech & Chong) Checked compression again and it was up to spec. Motor runs great now. While your results may vary, this might help. Look at it as a Hail Mary pass. It'll only cost about 7 bucks to try. By the way, that 35# figure on #1 ain't great but may just be a sticky or leaky valve. While I wouldn't make any bets on the outcome, its always been my policy to try the cheapest fix first.
Thanks for the reply and tip. I use Seafoam in my daily drivers. I will try the wet method test and the soaking.
Interesting that Sea Foam is well known in your part of the country. I owned a NAPA store in the 90's/00's and a guy from Minnesota stopped in to try to get me to sell for him. He had cases of product in his car and demonstrated it on my personal truck. I didn't buy a lot from traveling salesmen but he was so convincing I bought a case of 24. He explained that he had worked for OMC (Outboard Marine Corp) for 20+ years. OMC was having a lot of trouble with clogged fuel systems on new in stock motors back in the 50's. They would sit at warehouses and dealers and the fuel would evaporate, leaving the carb clogged with varnish. They tasked an in-house petroleum engineer with developing a fix and they came up with what would later be called Sea Foam. They used it in-house but never merchandised it. He retired from OMC and licensed distribution rights for the product. When I talked with him he was just getting the company off the ground. The interesting part to me is that he was able to take this product national with apparent success. I don't know if he still owns the company, don't even remember his name after 20+ years. This is one of the few additives I have seen that really does what it is advertised to do. I sold that first case of product in less than a week and ended up getting an average of about 5 cases a month drop shipped to my little store. It's the only additive I ever sold where almost everyone came back for more and commented on the good results they got. It not only cleans fuel systems, it frees stuck rings and valves. We always joked about "mechanic in a can" but this stuff is about as close as you can get. In case anybody thinks I'm shilling for the company I'm retired now and my store is closed thanks to Auto Zone and Advance Auto. So I got no dog in this fight. Just wanted to share a real success story of a little guy like us who made good.
If it isn't one thing it's another! I walked by the car today, glanced down at the motor and saw two wet spots on the driver's side of the block. I wiped them dry thinking they may have come from the rain we got yesterday. A little blew in under the shed roof. When I went back by a few minutes later both spots were wet again! I wiped them dry, stood there for just a minute and noticed water seeping out of the block! So. is this something that I could fix or should I just scrap this motor. I can get my hands on another straight 8 from a 1950 that runs. I sold a 4 door parts car to a guy that pulled the motor and rolled it into his shop. He has no plans for it and I can get it for a very good price.And, it has a rebuilt fuel pump and runs without smoking!
It’s never a bad idea to have an extra engine kicking around, I’d buy it. Also, did you do your compression test with the engine hot and with the throttle open? Sent from my iPhone using H.A.M.B.
The guy who has the motor is willing to trade it for a bent grille from my 50. No, I haven't done a hot compression or with the throttle open. But I did a test after squirting some oil in the low cylinders and it brought the compression up about 10PSI on each of the low cylinders. The number 1 cylinder was at 35psi and rose to almost 50. Numbers 4,6 &7 were at 55 and went to 65. They were the only cylinders I performed the wet test on. After the test I poured a concoction of acetone and ATF in each cylinder then re-installed the plugs finger tight. I will let that set for a week then check compression again.
I picked up the other motor Wednesday morning and did a compression test Wednesday evening. The lowest cylinder was number 1 and it had 120psi! The other 7 were between 125 and 130. I now have to do the test on the motor that is in my 50 to determine which car gets this hot rod one!
If you need the existing engine to get you by for a while, or maybe longer, you might try sealing the block with sodium silicate (water glass). Just make sure you don't have any coolant leaking into the crankcase. https://itstillruns.com/use-liquid-glass-seal-blown-2300964.html
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