Nothing Special Posted August 12 Share Posted August 12 this seems very similar in theory to modern trucks having the fpr cycle for two seconds or so to repressurize the fuel rail before starting the engine. with a carburetor being vented atmospherically, fuel vaporizes and dries out just sitting still. add summer heat in Texas. add heat from a 460 sized 200 plus degree heater and low carb fuel is certainty. with an electric pump a very simple mod is quite easy. adding a discrete "momentary contact" switch to bypass the key switch to run the tank pump a few seconds on demand does this same thing. the factory wants to only operate by the key for a few reasons, so they triggered it by the ecu via the fpr. When I first went back from fuel injection to a carb on Pluto I had the same kind of thing. If it was shut off hot and left to soak for a few minutes it would be flooded when I tried to restart. I could still start it by holding the throttle wide open while cranking to clear the flood, but it was annoying. At the time I had a low-pressure electric fuel pump, so I could shut it off. If I remembered to do that long enough before shutting the engine off it wouldn't flood. Now years later I'm back to a mechanical fuel pump so I can't shut it off. And I've rebuilt the carb once or twice. I'm back to the flooding, but not as bad as it was, so I'm living with it. .... with a carburetor being vented atmospherically, fuel vaporizes and dries out just sitting still. add summer heat in Texas. add heat from a 460 sized 200 plus degree heater and low carb fuel is certainty.... I don't think low fuel in the bowl was the problem, at least for me. If I let everything cool down it would start fine. I think what was happening was that the fuel was expanding as it heated up, sitting still in the carb after the engine was shut off. As it expanded it overfilled the bowl and pushed out of the vents, running down into the intake manifold. Give it enough time and it would evaporate, but otherwise it was way too rich and I needed to get rid of the excess gas before it would start. The trick to preventing the problem wasn't to start the fuel pump before starting the engine, it was to shut the pump off before shutting the engine off. In fact, Pluto would start right up without running the pump first most of the time when I did this. It was only if I shut the pump off something like a minute* before shutting the engine off that I'd have any low fuel problems. If it was less than that there'd still be plenty of gas in the bowl to get it running. * This was years ago, so I might not be remembering the actual time accurately. Maybe it was 45 seconds, maybe 30. But it was quite a while. And this was a 302, typically driving slow in my neighborhood or in a parking lit, right before shutting down, not on the freeway or somewhere that it would be using gas faster. Although I did shut the pump off on the freeway once to see how long it would take for the engine to die. It was over 20 seconds. Link to comment Share on other sites More sharing options...
mat in tn Posted August 12 Share Posted August 12 When I first went back from fuel injection to a carb on Pluto I had the same kind of thing. If it was shut off hot and left to soak for a few minutes it would be flooded when I tried to restart. I could still start it by holding the throttle wide open while cranking to clear the flood, but it was annoying. At the time I had a low-pressure electric fuel pump, so I could shut it off. If I remembered to do that long enough before shutting the engine off it wouldn't flood. Now years later I'm back to a mechanical fuel pump so I can't shut it off. And I've rebuilt the carb once or twice. I'm back to the flooding, but not as bad as it was, so I'm living with it. .... with a carburetor being vented atmospherically, fuel vaporizes and dries out just sitting still. add summer heat in Texas. add heat from a 460 sized 200 plus degree heater and low carb fuel is certainty.... I don't think low fuel in the bowl was the problem, at least for me. If I let everything cool down it would start fine. I think what was happening was that the fuel was expanding as it heated up, sitting still in the carb after the engine was shut off. As it expanded it overfilled the bowl and pushed out of the vents, running down into the intake manifold. Give it enough time and it would evaporate, but otherwise it was way too rich and I needed to get rid of the excess gas before it would start. The trick to preventing the problem wasn't to start the fuel pump before starting the engine, it was to shut the pump off before shutting the engine off. In fact, Pluto would start right up without running the pump first most of the time when I did this. It was only if I shut the pump off something like a minute* before shutting the engine off that I'd have any low fuel problems. If it was less than that there'd still be plenty of gas in the bowl to get it running. * This was years ago, so I might not be remembering the actual time accurately. Maybe it was 45 seconds, maybe 30. But it was quite a while. And this was a 302, typically driving slow in my neighborhood or in a parking lit, right before shutting down, not on the freeway or somewhere that it would be using gas faster. Although I did shut the pump off on the freeway once to see how long it would take for the engine to die. It was over 20 seconds. certainly, a problem to be addressed differently. lowering float level comes to mind. but everything has its limits. I have had one do something similar to this recently, but I had not looked for a wet intake frankly it was just too dang hot and so was I. Link to comment Share on other sites More sharing options...
viven44 Posted August 12 Share Posted August 12 The trick to preventing the problem wasn't to start the fuel pump before starting the engine, it was to shut the pump off before shutting the engine off. Yes I can attest to this. I can restart it without needing to run the pump... as long as the pump was turned off and the engine ran for an additional 10-15 secs -- no problems. In fact a couple of times I forgot to turn the pump on only for things to start stumbling like 20 secs later In my case "heat soak" meant the starter was unable to turn. I always understood that as ... the engine compression / pre-ignition fighting the starter. When this used to happen, if I tried to jump the starter without spark it would crank no problem, but if there was spark the starter had to fight hard before things would turn.... But as long as the bowl has been emptied slighty... all seems to be good Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 12 Share Posted August 12 The trick to preventing the problem wasn't to start the fuel pump before starting the engine, it was to shut the pump off before shutting the engine off. Yes I can attest to this. I can restart it without needing to run the pump... as long as the pump was turned off and the engine ran for an additional 10-15 secs -- no problems. In fact a couple of times I forgot to turn the pump on only for things to start stumbling like 20 secs later In my case "heat soak" meant the starter was unable to turn. I always understood that as ... the engine compression / pre-ignition fighting the starter. When this used to happen, if I tried to jump the starter without spark it would crank no problem, but if there was spark the starter had to fight hard before things would turn.... But as long as the bowl has been emptied slighty... all seems to be good And this is why timing retard is supposed to be built into the DS-II module. But as Gary can attest, not even all Motorcraft modules work properly. I have tested BOTH of my Echlin TP40 modules, and can actually see them retard with the timing light when power is applied to the proper wire. (W&R reverse at the plug, so colour is pointless ) Link to comment Share on other sites More sharing options...
viven44 Posted August 12 Share Posted August 12 And this is why timing retard is supposed to be built into the DS-II module. But as Gary can attest, not even all Motorcraft modules work properly. I have tested BOTH of my Echlin TP40 modules, and can actually see them retard with the timing light when power is applied to the proper wire. (W&R reverse at the plug, so colour is pointless ) I am still to test that, despite how easy it is to do that ... what I gathered is .... disconnect the starter trigger wire after starting the engine... apply 12v to the starter trigger wire... if retard works then the rpm should drop.... Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 12 Share Posted August 12 I am still to test that, despite how easy it is to do that ... what I gathered is .... disconnect the starter trigger wire after starting the engine... apply 12v to the starter trigger wire... if retard works then the rpm should drop.... Not the trigger (S) wire, the (I) fuselink. Depending on how the system is wired it may kick your fuel pump into overdrive. With a timing light you can actually see when the transistor is delayed. Gary measured it on his 'scope. Link to comment Share on other sites More sharing options...
mat in tn Posted August 13 Share Posted August 13 Not the trigger (S) wire, the (I) fuselink. Depending on how the system is wired it may kick your fuel pump into overdrive. With a timing light you can actually see when the transistor is delayed. Gary measured it on his 'scope. certainly not on my own truck today. but I was able to sign off on a couple of projects . one is a cougar that I have been doing over the past months. added an aod and had to revisit the od band. turned out to be well out of spec. new parts are not always right. so, I replaced it with another brand and voila'. cost me an extra day labor, fluid, and parts. but it is spot on now. I do not like returns for faults, but it can happen. the oddity is that it was great, and we drove it most of a tank over a couple weeks but no long drives. customer brought it back for a review saying it stayed in od longer than he expected. so, I handled it. Link to comment Share on other sites More sharing options...
viven44 Posted August 13 Share Posted August 13 Not the trigger (S) wire, the (I) fuselink. Depending on how the system is wired it may kick your fuel pump into overdrive. With a timing light you can actually see when the transistor is delayed. Gary measured it on his 'scope. You are right, in the back of my mind I haven't conducted this experiment because I have a working system today and I don't want to possibly affect something by trying this. Bench testing the module would be the way to go... I don't have a fancy scope though. Well I also just remembered my EVTM is wrong.. I had to swap my red and white wires vs what is shown in the image below... Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 13 Author Share Posted August 13 You are right, in the back of my mind I haven't conducted this experiment because I have a working system today and I don't want to possibly affect something by trying this. Bench testing the module would be the way to go... I don't have a fancy scope though. Well I also just remembered my EVTM is wrong.. I had to swap my red and white wires vs what is shown in the image below... Pull the R/LB wire off the starter relay and touch it to the post from the battery. That will feed power to the Ds-II module telling it you are cranking the engine and the timing should retard. Link to comment Share on other sites More sharing options...
viven44 Posted August 13 Share Posted August 13 certainly not on my own truck today. but I was able to sign off on a couple of projects . one is a cougar that I have been doing over the past months. added an aod and had to revisit the od band. turned out to be well out of spec. new parts are not always right. so, I replaced it with another brand and voila'. cost me an extra day labor, fluid, and parts. but it is spot on now. I do not like returns for faults, but it can happen. the oddity is that it was great, and we drove it most of a tank over a couple weeks but no long drives. customer brought it back for a review saying it stayed in od longer than he expected. so, I handled it. Staying in OD for longer than expected ? So it didn't downshift when it was supposed to ? That job would probably take me a few days, possibly a week ... And thanks Gary for that wiring diagram Link to comment Share on other sites More sharing options...
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