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87 D150 Stalling problems. Please help!
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Author:  ceej [ Thu Apr 02, 2009 8:40 pm ]
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Yes on the vacuum amplifier. They do fail. It's important that it is hooked up correctly to operate though. You'll need to go over your vacuum diagram for that vehicle to determine correct connections are made, and check the temperature vacuum switch for operation. (If that's what it uses.) Without the EGR you may need to take some timing out. With your particular distributor and configuration, I wouldn't know where to start.
Replace the sock if it's collapsing You don't want to suck big chunks up into your fuel line. Sounds like it's time to replace the fuel pickup anyway. Just make sure there is nothing that could be sucked off the bottom of the tank to plug it up.

-- If you have sensors that the ECM is looking for disconnected, it isn't going to work correctly.--

Get everything back to stock and start there, or you will have to make a decision on how you want to go about modifying things. As long as you are running the ECM, going to a different configuration without the associated equipment isn't going to net good results.

CJ

Author:  THOR [ Fri Apr 03, 2009 12:23 pm ]
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Quote:
When my truck is hot and I pump the gas it givesme that smoke also, so my guess would be the it was the fuel hitting a warm manifold and evaporating.
That's exactly right. The vapor you see coming from the carb is fuel that you just pumped into a hot manifold and it vaporized. Even right after a hot shutdown you will typically still get fuel vapors out through the carb bore. This is because of fuel that went into the manifold as the engine was spinning down to a stop after shutdown of the ignition system. Thats pretty much standard op for carbs.

Like Ceej said, if you are using the ECM, everything has to be plugged in and working correctly for the ECM to be able to control the ignition correctly.

If you want to check and see if the fuel pump is working, then just rev the engine in neutral. Since mechanical fuel pumps do not sense load, they should put out the same amount of fuel whether under a load or not. This will only work if you KNOW for a fact that the ignition system is working... as evidenced by full checks of the ignition with an oscilloscope.

When you placed the oscilloscope on the truck, did you check the primary AND secondary side? Also, did you only check at idle? Put the scope back on it, and run up to 3 or 4k RPM, see if it is still working properly if you have not done so already. A good coil will have at least 5 oscillations after the field has collapsed and the voltage flies out through the coil wire. Any less than 5 oscillations, and your coil is getting weak. Also make sure that the coil takes only a few milliseconds to charge up. If it takes too long to charge, then you won't have enough spark to fire the plug reliably.

If you want to rid your rig of the ECM and go with something you cannot plug a scan tool into, just convert it back to standard EI ignition and a standard vacuum/mechanical advance distributor, instead of the empty one you have in there.

~THOR~

Author:  Mister_Perkins [ Fri Apr 03, 2009 1:45 pm ]
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Okay. Well im lifting the truck up tomorrow and dropping the tank, removing the sock, and installing an electric fuel pump. Any other suggestions is greatly appreciated. Thanks!

Author:  Mister_Perkins [ Sun Apr 05, 2009 4:48 pm ]
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well didnt get a chance to get it up on the rack yet, but I did get a chance to install my new electronic fuel pump to take place of my mechanical. Now I know for sure that besides code 91 vaccume transistor circuit having a problem, my sending unit must have a hole in it. I limped back to the shop and parked it until i get a chance to get it up on the rack and drop the tank. Does anyone know where i can pick up a sending unit for my truck? I haven't called any parts stores yet, but I'm just guessing they dont carry it.

Author:  DonnieG [ Mon Apr 06, 2009 6:52 pm ]
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Look on Ebay, There two listed right now. You will need to know what size tank you have (20 30 Gal) they are different. Also you might try hooking the elect pump to a small gas can first. Could save the time and money of changing sending unit. Donnie

Author:  Mister_Perkins [ Mon Apr 06, 2009 7:02 pm ]
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I already using the electric pump to pump to a gas can. It was pumping all kinds of air. All of the fuel lines from pump > tank are new. So the only thing left is the sending unit. Can you give me a link for those sending units?

Author:  DonnieG [ Mon Apr 06, 2009 7:11 pm ]
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Go to Ebay, search "dodge truck sending unit" there are 11 .

Author:  Mister_Perkins [ Tue Apr 07, 2009 3:15 pm ]
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well, dropped the tank today and found the main supply line was almost completely pinched closed from the clamp I put on it. that would explain why it wasnt pushing the much pressure. Un-soldering the lines and resoldering new lines in it tomorrow. I'll update everyone

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