Tech Questions - Car Dies - Fuel Related?
My #3633, with a 351W, stroked to 427, had an occasional problem, usually after refueling, but is now constant. If I take it up to 3500-4000 rpm, it starts to die. Sometimes completely, sometimes where I have to pull off the road, wait a few minutes, then restart, but can barely keep it going. Pumping the accelerator, does no good. I cleaned and regaped the plugs to .40 (recommended for this engine), replaced the MSD cap, rotor, and magnetic pickup (with MSD parts), replaced the MSD 6AL module (10 years old) with a new one, new MSD coil (blaster model), new in line fuel filter (the pretty canister was empty, so added one) prior to the Holley electric fuel pump (which is pumping 10psi), checked the solid fuel lines going into a Holley 750-double pumper carb, and pulled the carb to inspect float tanks for debris (there wasn't any). Prior to removing, I checked the accelerator pumps, and they are squirting fuel fine. I plan to rebuild it anyway as soon as the new Holley kit arrives. Meanwhile, I drained most of the fuel from the tank and saw no evidence of water or debris. I took out all the screws from the tank sending unit with plans to remove that for a look at the 'pickup'. According to my Pantera manual, it should come out without removing the tank, but I am unable to get it past the white switch in that line. The car was restored in the late nineties, but pretty sure the tank is in the same location, so why won't it come out? The only other 'suspicious' thing (to me) is that I have a 'cap' on the top of the tank (part #7033006?), but that appears on the tank diagram in my book. I do NOT have a vapor separator assembly that went to a canister assembly on the original setup. I DO have a small 4-5" tube that faces down on the first 2" on the fuel filler pipe that (my guess) is acting as a vent to replace to vapor separator, since it is not shown on the filler tube in my repair manual. When cold, the car starts fine, even without a choke. I could drive it gently down the street, but then trying to go up a small hill it starts choking, then dies. Yes, I have about 7-8 gallons of premium fuel and an octane booster additive in the tank. So, IF I can get the sending unit out to check that, I will be at the limit of my mechanical knowledge and will likely have to tow it to a shop (somewhere in the Atlanta, GA. area), to be fixed unless one of you kind experts can tell me what else to check. Happy to provide my personal email or phone for a conversation outside of this POCA email string. Thanks for any assistance on getting the sending unit out or the main problem of stalling. My #3633, with a 351W, stroked to 427, had an occasional problem, usually after refueling, but is now constant. If I take it up to 3500-4000 rpm, it starts to die. Sometimes completely, sometimes where I have to pull off the road, wait a few minutes, then restart, but can barely keep it going. Pumping the accelerator, does no good. I cleaned and regaped the plugs to .40 (recommended for this engine), replaced the MSD cap, rotor, and magnetic pickup (with MSD parts), replaced the MSD 6AL module (10 years old) with a new one, new MSD coil (blaster model), new in line fuel filter (the pretty canister was empty, so added one) prior to the Holley electric fuel pump (which is pumping 10psi), checked the solid fuel lines going into a Holley 750-double pumper carb, and pulled the carb to inspect float tanks for debris (there wasn't any). Prior to removing, I checked the accelerator pumps, and they are squirting fuel fine. I plan to rebuild it anyway as soon as the new Holley kit arrives. Meanwhile, I drained most of the fuel from the tank and saw no evidence of water or debris. I took out all the screws from the tank sending unit with plans to remove that for a look at the 'pickup'. According to my Pantera manual, it should come out without removing the tank, but I am unable to get it past the white switch in that line. The car was restored in the late nineties, but pretty sure the tank is in the same location, so why won't it come out? The only other 'suspicious' thing (to me) is that I have a 'cap' on the top of the tank (part #7033006?), but that appears on the tank diagram in my book. I do NOT have a vapor separator assembly that went to a canister assembly on the original setup. I DO have a small 4-5" tube that faces down on the first 2" on the fuel filler pipe that (my guess) is acting as a vent to replace to vapor separator, since it is not shown on the filler tube in my repair manual. When cold, the car starts fine, even without a choke. I could drive it gently down the street, but then trying to go up a small hill it starts choking, then dies. Yes, I have about 7-8 gallons of premium fuel and an octane booster additive in the tank. So, IF I can get the sending unit out to check that, I will be at the limit of my mechanical knowledge and will likely have to tow it to a shop (somewhere in the Atlanta, GA. area), to be fixed unless one of you kind experts can tell me what else to check. Happy to provide my personal email or phone for a conversation outside of this POCA email string. Thanks for any assistance on getting the sending unit out or the main problem of stalling.
It’s always hard to diagnose from a distance and given you have checked and changed a large portion of potential culprits I’m really only clutching at straws for other things to investigate. From your description it sounds like it is failing under load which points more to electrical than fuel. 1. A fuel filter prior to the pump should be coarse (100 micron) after the fuel pump (40 micron). Generally one isn’t required prior to the pump as the tank pickup has a sock filter. Over time the sock can disintegrate and pose a restriction to flow. The fuel pickup and gauge float require to be rotated to extract from the tank, if I recall it’s a lot easier with the quarter window removed. 2. There is usually some form of filter at the carb inlets, perhaps a sintered metal one, so check and clean those if not done so already. 2. A bad voltage regulator can act to restrict rpm and or breakdown at high rpm as can a bad coil, but you already changed the latter. 3. Harmonic balancers can fail at the bonded outer to inner and slip, thus throwing timing off. 4. The distributor gear drive pin could be partially failed and allowed the gear to rotate slightly on the shaft throwing timing off. Have you checked ignition timing with a timing light? Julian
On Jul 12, 2025, at 07:52, Bill Cartus via DeTomaso <detomaso@detomasolist.com> wrote:
My #3633, with a 351W, stroked to 427, had an occasional problem, usually after refueling, but is now constant. If I take it up to 3500-4000 rpm, it starts to die. Sometimes completely, sometimes where I have to pull off the road, wait a few minutes, then restart, but can barely keep it going. Pumping the accelerator, does no good. I cleaned and regaped the plugs to .40 (recommended for this engine), replaced the MSD cap, rotor, and magnetic pickup (with MSD parts), replaced the MSD 6AL module (10 years old) with a new one, new MSD coil (blaster model), new in line fuel filter (the pretty canister was empty, so added one) prior to the Holley electric fuel pump (which is pumping 10psi), checked the solid fuel lines going into a Holley 750-double pumper carb, and pulled the carb to inspect float tanks for debris (there wasn't any). Prior to removing, I checked the accelerator pumps, and they are squirting fuel fine. I plan to rebuild it anyway as soon as the new Holley kit arrives. Meanwhile, I drained most of the fuel from the tank and saw no evidence of water or debris. I took out all the screws from the tank sending unit with plans to remove that for a look at the 'pickup'. According to my Pantera manual, it should come out without removing the tank, but I am unable to get it past the white switch in that line. The car was restored in the late nineties, but pretty sure the tank is in the same location, so why won't it come out? The only other 'suspicious' thing (to me) is that I have a 'cap' on the top of the tank (part #7033006?), but that appears on the tank diagram in my book. I do NOT have a vapor separator assembly that went to a canister assembly on the original setup. I DO have a small 4-5" tube that faces down on the first 2" on the fuel filler pipe that (my guess) is acting as a vent to replace to vapor separator, since it is not shown on the filler tube in my repair manual. When cold, the car starts fine, even without a choke. I could drive it gently down the street, but then trying to go up a small hill it starts choking, then dies. Yes, I have about 7-8 gallons of premium fuel and an octane booster additive in the tank. So, IF I can get the sending unit out to check that, I will be at the limit of my mechanical knowledge and will likely have to tow it to a shop (somewhere in the Atlanta, GA. area), to be fixed unless one of you kind experts can tell me what else to check. Happy to provide my personal email or phone for a conversation outside of this POCA email string. Thanks for any assistance on getting the sending unit out or the main problem of stalling.
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Two things to check electrically. 1 accessories off of the coil lead. If anything like electrical choke is connected to the coil wire, it won’t rev over 3500. 2 ground wire on accessory panel. There is a ground wire that attaches to the panel that the coil and voltage regulator mount to. Mine fell apart after I re-wired it once. It would start and would rev to 3000, then it would fall on its face. YMMV #6859 M Sent from tiny apple obfuscator.
On Jul 12, 2025, at 11:32 AM, Julian Kift <julian_kift@hotmail.com> wrote:
It’s always hard to diagnose from a distance and given you have checked and changed a large portion of potential culprits I’m really only clutching at straws for other things to investigate. From your description it sounds like it is failing under load which points more to electrical than fuel.
1. A fuel filter prior to the pump should be coarse (100 micron) after the fuel pump (40 micron). Generally one isn’t required prior to the pump as the tank pickup has a sock filter. Over time the sock can disintegrate and pose a restriction to flow. The fuel pickup and gauge float require to be rotated to extract from the tank, if I recall it’s a lot easier with the quarter window removed. 2. There is usually some form of filter at the carb inlets, perhaps a sintered metal one, so check and clean those if not done so already. 2. A bad voltage regulator can act to restrict rpm and or breakdown at high rpm as can a bad coil, but you already changed the latter. 3. Harmonic balancers can fail at the bonded outer to inner and slip, thus throwing timing off. 4. The distributor gear drive pin could be partially failed and allowed the gear to rotate slightly on the shaft throwing timing off. Have you checked ignition timing with a timing light?
Julian
On Jul 12, 2025, at 07:52, Bill Cartus via DeTomaso <detomaso@detomasolist.com> wrote:
My #3633, with a 351W, stroked to 427, had an occasional problem, usually after refueling, but is now constant. If I take it up to 3500-4000 rpm, it starts to die. Sometimes completely, sometimes where I have to pull off the road, wait a few minutes, then restart, but can barely keep it going. Pumping the accelerator, does no good. I cleaned and regaped the plugs to .40 (recommended for this engine), replaced the MSD cap, rotor, and magnetic pickup (with MSD parts), replaced the MSD 6AL module (10 years old) with a new one, new MSD coil (blaster model), new in line fuel filter (the pretty canister was empty, so added one) prior to the Holley electric fuel pump (which is pumping 10psi), checked the solid fuel lines going into a Holley 750-double pumper carb, and pulled the carb to inspect float tanks for debris (there wasn't any). Prior to removing, I checked the accelerator pumps, and they are squirting fuel fine. I plan to rebuild it anyway as soon as the new Holley kit arrives. Meanwhile, I drained most of the fuel from the tank and saw no evidence of water or debris. I took out all the screws from the tank sending unit with plans to remove that for a look at the 'pickup'. According to my Pantera manual, it should come out without removing the tank, but I am unable to get it past the white switch in that line. The car was restored in the late nineties, but pretty sure the tank is in the same location, so why won't it come out? The only other 'suspicious' thing (to me) is that I have a 'cap' on the top of the tank (part #7033006?), but that appears on the tank diagram in my book. I do NOT have a vapor separator assembly that went to a canister assembly on the original setup. I DO have a small 4-5" tube that faces down on the first 2" on the fuel filler pipe that (my guess) is acting as a vent to replace to vapor separator, since it is not shown on the filler tube in my repair manual. When cold, the car starts fine, even without a choke. I could drive it gently down the street, but then trying to go up a small hill it starts choking, then dies. Yes, I have about 7-8 gallons of premium fuel and an octane booster additive in the tank. So, IF I can get the sending unit out to check that, I will be at the limit of my mechanical knowledge and will likely have to tow it to a shop (somewhere in the Atlanta, GA. area), to be fixed unless one of you kind experts can tell me what else to check. Happy to provide my personal email or phone for a conversation outside of this POCA email string. Thanks for any assistance on getting the sending unit out or the main problem of stalling.
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Bill, For a completely different suggestion, I had a very similar scenario after I installed a different fuel tank. It ran fine at first but then began exhibiting the same symptoms you are describing. I had a pinhole rust hole in the fuel pickup halfway down the tank, so when the tank was full it ran fine but when the level got below that point it sucked air and gas together. That’s a very unlikely scenario but it costs nothing to throw a couple of gallons of additional fuel into the tank. If the problem temporarily goes away, you’ve found the likely culprit. And if not, you haven’t lost anything…. Mike Sent from my iPad
On Jul 12, 2025, at 17:31, Julian Kift <julian_kift@hotmail.com> wrote:
It’s always hard to diagnose from a distance and given you have checked and changed a large portion of potential culprits I’m really only clutching at straws for other things to investigate. From your description it sounds like it is failing under load which points more to electrical than fuel.
1. A fuel filter prior to the pump should be coarse (100 micron) after the fuel pump (40 micron). Generally one isn’t required prior to the pump as the tank pickup has a sock filter. Over time the sock can disintegrate and pose a restriction to flow. The fuel pickup and gauge float require to be rotated to extract from the tank, if I recall it’s a lot easier with the quarter window removed. 2. There is usually some form of filter at the carb inlets, perhaps a sintered metal one, so check and clean those if not done so already. 2. A bad voltage regulator can act to restrict rpm and or breakdown at high rpm as can a bad coil, but you already changed the latter. 3. Harmonic balancers can fail at the bonded outer to inner and slip, thus throwing timing off. 4. The distributor gear drive pin could be partially failed and allowed the gear to rotate slightly on the shaft throwing timing off. Have you checked ignition timing with a timing light?
Julian
On Jul 12, 2025, at 07:52, Bill Cartus via DeTomaso <detomaso@detomasolist.com> wrote:
My #3633, with a 351W, stroked to 427, had an occasional problem, usually after refueling, but is now constant. If I take it up to 3500-4000 rpm, it starts to die. Sometimes completely, sometimes where I have to pull off the road, wait a few minutes, then restart, but can barely keep it going. Pumping the accelerator, does no good. I cleaned and regaped the plugs to .40 (recommended for this engine), replaced the MSD cap, rotor, and magnetic pickup (with MSD parts), replaced the MSD 6AL module (10 years old) with a new one, new MSD coil (blaster model), new in line fuel filter (the pretty canister was empty, so added one) prior to the Holley electric fuel pump (which is pumping 10psi), checked the solid fuel lines going into a Holley 750-double pumper carb, and pulled the carb to inspect float tanks for debris (there wasn't any). Prior to removing, I checked the accelerator pumps, and they are squirting fuel fine. I plan to rebuild it anyway as soon as the new Holley kit arrives. Meanwhile, I drained most of the fuel from the tank and saw no evidence of water or debris. I took out all the screws from the tank sending unit with plans to remove that for a look at the 'pickup'. According to my Pantera manual, it should come out without removing the tank, but I am unable to get it past the white switch in that line. The car was restored in the late nineties, but pretty sure the tank is in the same location, so why won't it come out? The only other 'suspicious' thing (to me) is that I have a 'cap' on the top of the tank (part #7033006?), but that appears on the tank diagram in my book. I do NOT have a vapor separator assembly that went to a canister assembly on the original setup. I DO have a small 4-5" tube that faces down on the first 2" on the fuel filler pipe that (my guess) is acting as a vent to replace to vapor separator, since it is not shown on the filler tube in my repair manual. When cold, the car starts fine, even without a choke. I could drive it gently down the street, but then trying to go up a small hill it starts choking, then dies. Yes, I have about 7-8 gallons of premium fuel and an octane booster additive in the tank. So, IF I can get the sending unit out to check that, I will be at the limit of my mechanical knowledge and will likely have to tow it to a shop (somewhere in the Atlanta, GA. area), to be fixed unless one of you kind experts can tell me what else to check. Happy to provide my personal email or phone for a conversation outside of this POCA email string. Thanks for any assistance on getting the sending unit out or the main problem of stalling.
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Detomaso Email List is not managed by POCA Posted emails must not exceed 1.5 Megabytes DeTomaso mailing list DeTomaso@server.detomasolist.com http://server.detomasolist.com/mailman/listinfo/detomaso
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participants (4)
-
Bill Cartus -
Julian Kift -
Mike Drew -
Mirrilm Earthlink