AeroNautical Posted February 10, 2020 Share Posted February 10, 2020 This issue just started a few days ago. After the truck has been running awhile, and shut it off, if you turn it back on it will run incredibly rich, stumble and then die. BUT, after 10 seconds of that, giving a bit of gas, it runs perfectly smooth and fine. Truck details in my signature, and NO major changes or mods lately to have caused it. I thought at first it was vapor lock, so I got a heat shield kit for it. Also checked the fuel rail valve for liquid gas when the problem would happen. It's not vapor lock. All sensors are brand new due to the obd1 conversion I did over a year ago. Ran great until a few days ago. Ideas? Thanks. The heat shield I installed: Link to comment Share on other sites More sharing options...
Warren Mohler Posted February 11, 2020 Share Posted February 11, 2020 Check fuel pressure reg. for leak to vac. hose Link to comment Share on other sites More sharing options...
Eagle Posted February 11, 2020 Share Posted February 11, 2020 Also check CPS -- could be failing in heat soak. Link to comment Share on other sites More sharing options...
Ωhm Posted February 11, 2020 Share Posted February 11, 2020 Leaky injector(s). Check fuel rail for loss of pressure when engine is OFF. Link to comment Share on other sites More sharing options...
AeroNautical Posted February 11, 2020 Author Share Posted February 11, 2020 Checked injectors, no leaks I can see or smell. Pressure at rail is correct, about 40 psi with the engine off. I'd think it wouldn't correct itself if it were leaking or low pressure, fuel delivery is good. As for the CPS, I've had no crank conditions on a heat soaked CPS, back when it was RENIX. It would just crank and crank, until it cooled enough to actually start. This starts every time, and with slight pressure on the gas pedal, stays on. Then after about 10 seconds, you can release the skinny pedal and it runs perfectly. Link to comment Share on other sites More sharing options...
omega_rugal Posted February 11, 2020 Share Posted February 11, 2020 so.. -runs fine for 10 mins - next start goes too rich and floods - 10 seconds later starts normally what happens if you try the ´flood clear´ method? have you checked if the IAC opens properly? this one likes to stick leaving only fuel and no air in the manifold... Link to comment Share on other sites More sharing options...
AeroNautical Posted February 11, 2020 Author Share Posted February 11, 2020 12 hours ago, omega_rugal said: so.. -runs fine for 10 mins - next start goes too rich and floods - 10 seconds later starts normally what happens if you try the ´flood clear´ method? have you checked if the IAC opens properly? this one likes to stick leaving only fuel and no air in the manifold... Not exactly. Like this: -starts and runs fine from cold, no matter how long you run it. -next start when hot, is too rich and stumbles, but give it some gas and in 10 seconds it corrects itself and runs fine I'm unfamiliar with the "flood clear" method, what do I do? Didn't think a fuel injection system could flood like that Link to comment Share on other sites More sharing options...
omega_rugal Posted February 11, 2020 Share Posted February 11, 2020 to clear a flooded 4.0 you crank it while presssing the accelerator all the way down, this shuts down the injectors and allows more air to wash away the extra gasoline Link to comment Share on other sites More sharing options...
AeroNautical Posted February 12, 2020 Author Share Posted February 12, 2020 4 hours ago, omega_rugal said: to clear a flooded 4.0 you crank it while presssing the accelerator all the way down, this shuts down the injectors and allows more air to wash away the extra gasoline I didn't know this, thanks. Next time it gives me issues, I'll try this and see if it alleviates it. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 12, 2020 Share Posted February 12, 2020 How long does the system hold the 40 PSI after shutoff? Link to comment Share on other sites More sharing options...
AeroNautical Posted February 12, 2020 Author Share Posted February 12, 2020 3 hours ago, cruiser54 said: How long does the system hold the 40 PSI after shutoff? In 5 minutes with the pump off it drops to about 39 psi Link to comment Share on other sites More sharing options...
cruiser54 Posted February 12, 2020 Share Posted February 12, 2020 Go 30 minutes. Link to comment Share on other sites More sharing options...
AeroNautical Posted February 12, 2020 Author Share Posted February 12, 2020 4 hours ago, cruiser54 said: Go 30 minutes. Roger, next chance I get. I guess that would localize an injector leaking into the cylinder? Link to comment Share on other sites More sharing options...
cruiser54 Posted February 12, 2020 Share Posted February 12, 2020 2 minutes ago, PFCLeist said: Roger, next chance I get. I guess that would localize an injector leaking into the cylinder? Maybe more than one...... Link to comment Share on other sites More sharing options...
AeroNautical Posted February 13, 2020 Author Share Posted February 13, 2020 20 hours ago, cruiser54 said: Maybe more than one...... Started at 38 PSI, waited 30 minutes, read 20 PSI. Pump off for the test. Bad injector? Link to comment Share on other sites More sharing options...
Ωhm Posted February 13, 2020 Share Posted February 13, 2020 Three (3) things hold fuel rail pressure. Check ball at the fuel pump. Leak here doesn't fit the symptom. Fuel Pressure Regulator (FPR), check for fuel in the vacuum hose between FPR and intake manifold. That leaves leaky injector(s). Link to comment Share on other sites More sharing options...
AeroNautical Posted February 13, 2020 Author Share Posted February 13, 2020 37 minutes ago, Ωhm said: Three (3) things hold fuel rail pressure. Check ball at the fuel pump. Leak here doesn't fit the symptom. Fuel Pressure Regulator (FPR), check for fuel in the vacuum hose between FPR and intake manifold. That leaves leaky injector(s). FPR vacuum line is dry, nor does it smell like fuel. I pulled the rail with injectors attached, turned fuel pump on, and none are leaking at all. Link to comment Share on other sites More sharing options...
Ωhm Posted February 13, 2020 Share Posted February 13, 2020 Man, it just sounds like excess of fuel, leaking between STARTS. Link to comment Share on other sites More sharing options...
AeroNautical Posted February 14, 2020 Author Share Posted February 14, 2020 2 hours ago, Ωhm said: Man, it just sounds like excess of fuel, leaking between STARTS. Yeah, your right. Or an injector is held open during start. I ran a 9 volt through each injector while the rail was off to make sure it sprayed and didn't get stuck, and still worked perfectly. It's a rough start, too, vibrates like hell. Then it just magically fixes itself, haha. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 14, 2020 Share Posted February 14, 2020 Original injectors? Link to comment Share on other sites More sharing options...
AeroNautical Posted February 14, 2020 Author Share Posted February 14, 2020 1 hour ago, cruiser54 said: Original injectors? Mustang 24 lbs injectors I've been running for a little while now, much longer than when these issues came up. Link to comment Share on other sites More sharing options...
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