The other night I get a call from a buddy. His son has taken his 23 to a show and got stranded on the way home (after dark of course). I throw some tools and a light in the truck and head out to see if I can help...It will be hours before the tow truck arrives anyway. This is an early flathead with Helmet distributor, twin big 97's, electric fuel pump, Holley pressure regulator. Car has run great for a few years, I put a new fuel pump and filter on it at the beginning of summer and it has run a bunch of trouble free miles since. Other than that there have been no issues. I get on site (side of an interstate just beyond the on ramp...in the dark) and the Son reports that he was accelerating up the ramp and it started to run like crap, lost power and quit. He "fiddled" with a few things on the carbs but it didn't help. Car is running straight linkage so my initial thought was maybe one of the linkage clamps was slipping on the shaft. I did a light limited visual inspection and everything seemed to be working as it should I had him try and start it and it cranked and cranked and eventually started but was running very rough and would only stay running with constant hand manipulation of the linkage. If the RPM's came back down to near idle and you left it alone it would die. Also the rear carb sounded like a giant vacuum leak compared to the front carb. We decided that it wasn't going to get fixed on the side of the interstate in the dark so we waited for the tow truck. I am going over there tomorrow to have a look at it in the garage and I have been overthinking this thing to death. I have considered everything from points, condenser, coil, to fuel starvation, blown pressure regulator, power valve, etc. And come up with reasons it could or couldn't be any of those things...lol. Anyone ever had this happen? Suggestions where to start looking? thanks. Chappy
If the rear carb sounds like a vacuum leak, start there . coild be a blown gasket , power valve , line off etc etc
Could be several different things, but as above poster noted I would start at the carbs first. You noted an obvious issue. If a single carb is sucking that hard on a flatty with dual carbs and straight linkage I would start there before fiddling with anything else. Could be something as simple as the carbs being out of sync, and thats an easy preliminary check and fix. Start there and move on if that isn’t it.
whenever there is a running issue with multiple carbs, i like to bring back to just one carb to diagnose. if you dont have one make a block off plate for the rear carb, remove the rear carb and seal it off. See if it will fire now. Then you can check ignition stuff if there is still an issue. its just narrowing down the possible variables.
While engine s NOT running I would look down both carbs while moving the throttle arms. Make sure you are getting a squirt of fuel down the throat of the carb. If no squirt, start looking for fuel starvation issues.
Junk in the tank made its way to the carb? Some intakes don't have a common plenum so both carbs are required to feed all cylinders. Strombergs don't have a power valve that will "blow". Might get junk stuck in it, but if stuck open it just feeds extra gas. If stuck closed it should operate as fine from low RPM to mid.
after some more troubleshooting we realized that the fuel pump (in line electric) wasn't working correctly. I have never seen this exact symptom before. When power is applied to the pump (key on) the pump will pump once or twice then stop (recreated on the bench after removal) until power is removed... then the next time power is applied it will pump once or twice then stop until power is removed. The pump was replaced with a similar pump. The new pump seemed to solve the issue for about 5 minutes. Now the new pump is acting exactly like the old pump. Full disclosure, both pumps are China made. I have found a Canada made Delphi pump to put on but I want to make sure that I don't have another problem that is burning up pumps. I am willing to accept that it is just cheap Chinese crap pumps. I checked everything else i could think of: tank is clean (hand made and new), new filter installed with each pump, pressure regulator is good (allows strong flow), voltage is pretty steady at 12.3V Should I consider adding an inline fuse to the pump power line? The original ran for 5 years without one.... Thanks again for all of the input. Chappy
Many years ago I had a on/off switch inline with the power to my electric pump. I was having problems with the engine shutting off a few miles driving. I removed the switch. No problems after that. I'm not sure if the switch wasn't rated for the amperage required, and might have been overheated and opening. I was just happy to "fix" the problem. Do you have a switch in your line that could be the problem?
Thanks Alchemy, There is no switch other than ignition. Pump gets its power from one of the switched circuits that comes on when the key goes to run. Haven't really dug to deep into that as it was working fine for a few years in this configuration. Chappy
Fuses are completely useless, all the way until there's an electrical problem that causes higher current than the circuit can handle. When that happens, if there is a fuse that will blow and all is well - except for someone scratching their head and trying to figure out what's wrong. When it happens and there isn't a fuse in the circuit wires get barbecued, possibly setting the entire car on fire, along with the garage it's in, the other cars in the garage, the house the garage stands next to, and a million acres of dry summer forest... All right, it isn't likely to go that horribly wrong, but it CAN happen, and even if it stops at a destroyed wiring harness that can be bad enough to fix. You don't miss a fuse before you need it. You never need most fuses, they just get installed and sit there until the car goes to the scrappers, but they just cost cents and reduce the problems that come IF there is a problem.
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