OT Dodge pickup help

Need help please. I have a 1990 Dodge 4x4 that I have had since new. Excellent condition in and out. Truck will not start without the carb ( throttle body injection) being primed. After primed start will run great. What gives??? 240.000 miles .
 
You either have a poor/bad fuel pump, or a line with a pin hole. If the line had a hole in it, you should smell gas. I am leaning towards a bad fuel pump.
 
I vote fuel pump... my 94 is on it's 3rd at 140k. There are several parts to them, strainer, pump, regulator and check valve are the important ones that come to mind. Failure of any of those could cause your problem.

Not a bad job if you unbolt the box and raise it.
 
Hello Richard from SE AZ,

probably the throttle position sensor. Bet you it runs good except for not staring. I don't know if it has one though. That is my guess

Guido.
 

The OP said the truck runs fine after it starts...that pretty much rules out the fuel pump wouldn't you think?

If I had to guess...and guess is all I can do because I am nowhere near the truck...I would guess that the fuel pump is not being energized when the engine is being cranked but when fuel is manually put into the throttle body, the engine fires and the key is released and returns to the run position at which point the fuel pump is energized and the engine continues to run.

I would look for voltage on the fuel pump hot wire while cranking before doing anything else.

The OP doesn't say if this is the first start of the day problem or a everytime start problem. For example, if the truck is started then driven 5 miles and shut off, does it have to be primed again to start again?
 
Thanks guys, Gonna look at and try to rule out all suggestions. Throttle position sensor is something new to me. I'll see if it has one. Replacing the fuel pump will be easy, I have the means to raise the bed.
 
(quoted from post at 23:18:37 04/11/15)
The OP said the truck runs fine after it starts...that pretty much rules out the fuel pump wouldn't you think?

One would think... but if the check valve is faulty? Hope he lets us know what he finds, trouble shooting after carbs and points went away can be a tough sometimes.
 
Not sure if Dodges have a fuel pump prime relay, but I know GM trucks had them, and was an issue on one I had. Aside from that, my vote is either a relay (energized pump to prime), or the pump. I had a bad fuel pump that also needed a squirt of fuel into the throttle body prior to starting, and once it fired it would run until turned off. Replaced pump, problem gone.
 
I do know that a weak fuel pump will keep it running, but not have enough pressure to get it to start.

Just a guess without being there.....
 
(quoted from post at 03:36:02 04/12/15) Thanks guys, Gonna look at and try to rule out all suggestions. Throttle position sensor is something new to me. I'll see if it has one. Replacing the fuel pump will be easy, I have the means to raise the bed.

[b:260135c2f6]Do you have to prime it for every start or just after sitting overnight?

Can you hear the fuel pump run for 3 or 4 seconds when you turn the key on?[/b:260135c2f6]

I've never seen a weak fuel pump cause a no start and then run normally after pouring fuel into the throttle body.

Think about it, it doesn't take a lot of pressure to get enough fuel to start and idle but it sure does take normal pressure to accelerate and drive at highway speeds.
 
(quoted from post at 12:38:38 04/12/15) I do know that a weak fuel pump will keep it running, but not have enough pressure to get it to start.

Just a guess without being there.....

I can't agree with that at all. Just the opposite in fact.
 
TBI engines have an electric pump in the tank. So the diagnostic and symptoms are different than a mechanical pump like the carb'd engines had.

I've got the fsm. You can get them from Geno's Garage on CD for about $35-$40.
 
Something here to add.....
While I am not "expert" on Dodge systems, I HAVE been to most of Ford's engine/drivability schools. One thing that may be common to all of them is the "clear flood" mode. What that does is to shut off the injectors if the TP sensor voltage is over a certain threshold. On Ford vehicles, I think that the threshold voltage is around 2.0 volts. When the ECU sees voltage at this level, it considers the engine to be flooded, and turns off the injectors. I have encountered this several times on cars that would not start when they were cold. Just something to check. Also noted that this condition did not cause a trouble code.
I would check the TP sensor voltage under the condition when it will not start without a prime. If it is over 1 volt, I would suspect the sensor.
As others have said, I don't see a fuel pump as the cause. BUT - it would not hurt to also check the fuel pressure during the no-start condition. Might at least allow you to eliminate one potential cause.
 

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