Mechanics

FUEL PUMP RELAY OR ASD RELAY PROBLEM?

1999 Dodge Ram

Electrical problem
1999 Dodge Ram V8 Two Wheel Drive Automatic 167000 miles

I recently have had random shutdowns while driving my truck. Driving along at 55 mph and all the sudden a loss of power. Pull over to the side. I turned key off then on again and it started.

A few blocks down the road it did it again very quickly though. It lost power (like not getting fuel) slowed down and then it came back and I continued on to the gas station. I thought fuel problem (3/4 of tank of gas) so I got some STP gas treatment at the station.

No problems for a couple of days and then all of the sudden it did it again. This time it would not come back on. I was thinking fuel pump. But I noticed something strange. When I would turn the key to the ON position all the gauges (gas gauge / oil gauge / battery gauge) would move a little but go back to the flat position. This made me think it was some sort of electrical or relay problem. I opened the hood and found the relay box and just gently tapped on the top of the relays etc.

I got back in the car and when I turned the key to the ON position all my gauges were working (coincidence? ). The truck started and worked fine.

Is there something other than a relay that can cause this kind of symptom. If the Relay is bad would it cause the fuel gauge to not respond?

Thanks
Avatar
Tlgarrison
July 8, 2010.




First, the ASD will shut down spark to the engine as well as fuel. If it fails to start but the starter cranks the engine, it's not the ASD. As far as the gauges, that is odd. Did you ever notice it when you were having the problem?

Initially, it sounds like a bad fuel pump. However, check all the relays to make sure there is good contact and no corrosion. Especially check the fuel pump relay. Check under the power distribution box to make sure everything is tight.

Let me know. If all looks good, I will provide directions for checking fuel pump pressure.

Let me know what you find.

Joe

Checked the Relays, and under the box I don't see any corrosion or anything that is loose.

When problem happened last time: 1) Lost power (like out of gas)

2) would not start but starter would crank.

3) Gauges. Fuel gauge would not register fuel but power was going to the gauges. When I turned the ignition to on the fuel gauge would rise 1/8th of an inch but then drop back down. After messing with relays etc (about 5 minutes). I turned Ignition to On and the gauge worked and then the truck would start.

That was yesterday and it has not happened since.

After reading your message, I am wondering if it is electrical. Is their something under the dash or in the steering column that if it were to short would cause the symptoms I have described?

If the fuel pump is bad will you still have fuel reading on the dashboard gauge? Or is that controlled by a different mechanism?
AD

Tiny
Tlgarrison
Jul 8, 2010.
It does sounds electrical, and nothing on the steering column (other than the ignition switch). Keep in mind, the fuel float gauge that sends a signal to the gauge is a on piece unit with the fuel pump. Something tells me the relay that you tapped on wasn't making a good connection or the relay itself may be going bad. That is where I would start. Remove the relay, take some fine sand paper and shine up the connections so you know they are good. You may even want to get a new relay or switch it with one from the relay block that has the same part number just to see if it happens again.

Try that and let me know. Also, if it continues, I would first make sure the fuel pump isn't working. If it isn't, remove the tank and check the electrical connections to the pump. The ones on the tank are more likely to corrode because of location.

If you have other questions, let me know.
Joe

I tried cleaning connectors, swapped relays.

Drove fine since July 7th.

It happened again today July 13th. This time it provided me with another clue. I notice where the odemeter readout is, the words " no bus".

I opened the hood and messed with relays and nothing happened. I turned key off then on again and odometer was normal but fuel gauge did not read anything. I plugged in my code reader and waited and then the odometer read " no bus" again.

I figure that it is the pcm or the connections to it. So I took my screwdriver and lightly tapped a small black box that is located behind the Relay box (Is that the PCM?)

I got in and turned the key to on and the fuel gauge went up. Truck started.

Is there something I can do to check the connections and rule out that the pcm (computer) is bad?

Anything else I should check given this new clue?

Tiny
Tlgarrison
Jul 13, 2010.
That is a good clue. The no bus indicates there is no communication between the PCM and its components. Just remove the wiring harness to it and check for corrosion and make sure everything is tight.

Let me know what you find.

Joe
PS: I believe what you described is the PCM and usually they are either good or bad, so my guess is a bad connection or broken wire.

Found the problem!!! It was the "Engine InLine" Plug that plugs into the black fuse box under the hood that houses the Relays etc. See picture (top left hand corner of box).

I unscrewed the screw (noticed it was a little loose). cleaned contacts on the pins with contact cleaner and then applied dialectric grease to the contacts; screwed it back in place and it has been running like a top ever since. This is one for the books!!!

Thanks for all the help. This is a great site!


http://www.2carpros.com/forum/automotive_pictures/547721_EngineInline_1.jpg


Tiny
Tlgarrison
Jul 22, 2010.
Great job. That is what was causing the no bus signal. Thanks for using 2carpros. Com, and let us know if you have questions in the future.

Joe


AD