1990 w250 tbfi issue

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TonyU

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Ram Year
1990
Engine
5.9 gas
I will admit I am not a big mopar guy. I own a 1985 b350 and have a 1997 12 valve stuffed into a 73 chev 3/4 ton. I am a diesel and heavy equipment mech. I have a friend who has a 90 w250 with a 5.9 gas the managed to corrode the softplug in the back or the block out. Engine had several leaks and to help him out I opted to pull motor and fix all the leaks instead of droppinv trans and just fixinv the one soft plug. Motor ran fine before I pulled it. But after reinstalling it is very hard starting . And almost acts like there is a timming issue. I noticed as I was shutting down for the evening that with the key on the injectors onthe throttle body are spraying. With out the motor running and also noticed that when it is running at about 1/4 tthrottle (only place it will stay running) that they are pulsing and not spraying. My first thought was I hooked something up backwords but realized that can not really be done. I honestly know little about mopar and less about tbi any ideas what would cause this? I thought cam or crank sensor but realizex this motor had neither to hook up. What tells the injector when to fire. When to pulse and when to give a full spray??
 

crazzywolfie

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81 93
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5.2
there is a hall effect sensor in the distributor that tells the computer when to pulse the injectors. could have gone bad.
 
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TonyU

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Might also explain why the timing seems a little off. Maybe hot some moisture in the distributer while cleaning and degreasing. Will check this since I cant seem to find anything else..
 
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TonyU

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Replaced pickup coil. Even though it appeared to be working. Figured for $30 it couldnt hurt. Turned key on to bump motor to tdc to restab distributor and injectors still pulsing even with out pickup coil not plugged in. Ive spoke with two other mechanics I know and they have never heard of this.. any ideas guys??
 

crazzywolfie

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it might have just been a small squirt to get it started just like the fuel pump also runs for a couple seconds when you turn the key to the run position. now i don't know if you noticed it or not but the distributor either drops in dead on or 180* off so you didn't need to bring the engine to TDC.
 
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TonyU

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5.9 gas
Yes I did notice that handy little feature to the distributor. And its not just a squirt. It is pulsing. And giving a good shot about every second or less. Its giving a good cone when it shoots and about a good teaspoon full. The thing that is really confusing me is that it is doing it with the key in the run position and the motor not running. There should be nothing telling it to squirt without the motor sspinning. Im going to disconnect everything today and start hooking back up see if somehow I did get something wrong. But each connecter is idiot proof and each is a different shape or size
 

crazzywolfie

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ya something don't sound right. i am not really sure what would cause it to do that.
 
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TonyU

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Well I found the problem. At first I thought the map sensor was just really messed up and sending really bad voltages. When I tested it I was getting 2.5 volts no matter the vacuum. So replaced it and was getting the same so started chasing wires and realized the tps and the map right above and below each other have the exact same connection. Only difference is one pig tail is gray and one is black. And who would have thought they gray pigtail didnt go into the gray tps. and the black pig tail didnt go into the black map.. live and learn. On the bright side while chasing wires and testing things. I found two more vacuum leaks and the truck is running better than ever. Fuel milage is also up. Made a 150 mile round trip with it today putting in just over ten gallons of 92 and still have more fuel in it than when I hit the fuel stop. That trip before took almost 1/2 tank.. guessing its doing close to 18 where before it was doing 10. Have to do alot of running this coming week. Will fill it up (ouch) and see what she really does.. Thanks for the input
 
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