Bad fuel pump, regulator or relay????

gnxtc2 · Sep 11, 2014

For the past few weeks when I'm cruising, I am getting a surge. No drop in rpms, no boost change.....just a surge. I changed my fuel filters as a precaution.

Well this evening when I was driving home from my shop, I was pulling a small incline. Then all of a sudden, the motor starts bucking, like it was running out of fuel. I would occasionally surge for the ride home.

I get home and I look under the hood at fuel pressure gauge. I have a fuel pressure gauge to mount in the pod but haven't gotten around to it. Fuel pressure gauge said it was 40lbs.

As it idling in my driveway, it's surging/rpms changing. Thinking it a wiring issue, I wiggle the wires by the relay...no change.

I adjust the fuel pressure regulator to 65lbs.

I believe I have a Phoenix fuel pressure regulator that came in the E-Fuel kit from DynoProven. Not saying that it's DynoProven fault, any feedback on the Phoenix regulator?

I am running a SD Fuel pump that I bought new. It has around 12K miles on it. I don't even hear the fuel pump run if that means anything.

Thanks

Billy T.
[email protected]

silverpsd_06 · Sep 12, 2014

Sounds more like a hpo issue is causing the surging, check the IPR wiring or the ICP sensor.

co04cobra · Sep 12, 2014

You need to monitor the fuel pressure under load to be certain its not dropping. Also 40lbs seems a little low on the regulator. Did you set it there?

Arisley · Sep 12, 2014

I also agree on the 40 lbs. Regulators are two simple to fail, unless something breaks.
Relays either work or don't work, you would either get full power or no power. It can switch on and off, but not half way on.
Fuel pumps, however do get weak. It could also be supply. check fuel flow to the pump.

gnxtc2 · Sep 12, 2014

co04cobra said:
You need to monitor the fuel pressure under load to be certain its not dropping. Also 40lbs seems a little low on the regulator. Did you set it there?

No, I had it set at 65lbs.

Billy T.
[email protected]

gnxtc2 · Sep 12, 2014

Arisley said:
I also agree on the 40 lbs. Regulators are two simple to fail, unless something breaks.
Relays either work or don't work, you would either get full power or no power. It can switch on and off, but not half way on.
Fuel pumps, however do get weak. It could also be supply. check fuel flow to the pump.

Yea, that's what I thought about relays.
The set up was working flawlessly until now. Is it possible that the SD fuel pump is starting to go bad so soon?

Billy T.
[email protected]

Arisley · Sep 12, 2014

That or the supply is plugged at the tank. I had that issue, was driving me batty until I noticed no fuel flow from tank. Pickup foot broke in a billion pieces and clogged the line.

gnxtc2 · Sep 12, 2014

I'll have to switch tanks and see if it does it on the front tank. Not looking forward to dropping the rear tank.

Oh yea.... I did this bone head maneuver the other day when I was changing the oil. I shut the ball valve prior to the filters to change the fuel filters. Well, I never changed the fuel filters and started to drive the truck. Motor started bucking then I realized that I forgot to open the valve. Could I have ruined the pump by running it dry? Yea I know about the injectors. Motor never stopped running.

Billy T.
[email protected]

co04cobra · Sep 12, 2014

gnxtc2 said:
I'll have to switch tanks and see if it does it on the front tank. Not looking forward to dropping the rear tank.

Oh yea.... I did this bone head maneuver the other day when I was changing the oil. I shut the ball valve prior to the filters to change the fuel filters. Well, I never changed the fuel filters and started to drive the truck. Motor started bucking then I realized that I forgot to open the valve. Could I have ruined the pump by running it dry? Yea I know about the injectors. Motor never stopped running.

Billy T.
[email protected]

If you run it dry it is possible that did damage to the pump. Typically stock SD pumps are extremely durable though. Is a stock SD pump? or walboro?

gnxtc2 · Sep 12, 2014

Stock SD pump, bought it brand new. I set my fuel pressure before going to bed. Drove to work and the motor was more responsive/peppy.

I have to hook up the FP gauge so I know what's going on.

I have a brand new Walbro back up pump. I also ordered a Bosch replacement pump from Rock Auto they're cheap enough, just in case. I'd rather try a different pump before dropping my rear tank.

Arisley · Sep 12, 2014

Probably a good bet. Good luck.

I keep forgetting you have a OBS. Pretty much a superduty except for the body.

gnxtc2 · Sep 12, 2014

UPDATE:

Stopped by my friend's diesel shop. I popped the hood and the fuel pressure is now 75lbs according to the gauge on the FPR. Told him what was going on. He put an inline gauge (Snap-On) after the pump. It was reading 85lbs.

I then go in the truck and start power braking. The fuel pressure by the pump goes to 0. The truck was still running on 0 pressure. To confirm his gauge, I saw 0 pressure by the FPR.

We started checking for power at the pump. He disconnects the connector by the pump and checks for voltage.....nothing. Yes, the truck is still running, don't ask me how. We go under the hood and check the relay. There was no power on the load side of the relay. Then check for voltage on control/coil side of the relay...nothing.

I have a Standard Ignition NO/NC oil pressure switch installed by the oil filter head. The NC side is connected to the little wire on the starter relay. The NO is connected to the former fuel heater wire. The common goes to the coil of the relay. He wiggles the terminals on oil pressure switch and you can see the fuel pressure jumping. Bad oil pressure switch.

I jump out the oil pressure switch. The fuel heater wire (IGN power) is now connected directly to the coil of the relay. Motor sounds smoother. Checked the fuel pressure gauges, by the pump it was 85 and up by the FPR was 80; more like it. I backed the FP down to 65.

What has me stumped, the motor was running without the pump. If I didn't see it with my own eyes, I would never have believed it. There was 0 pressure and the pump disconnected. Was it running on vacuum?

Probably get rid of the oil pressure switch and go with an enertia switch from a Crown Vic.

Billy T.
[email protected]

lincolnlocker · Sep 12, 2014

gnxtc2 said:
UPDATE:

Stopped by my friend's diesel shop. I popped the hood and the fuel pressure is now 75lbs according to the gauge on the FPR. Told him what was going on. He put an inline gauge (Snap-On) after the pump. It was reading 85lbs.

I then go in the truck and start power braking. The fuel pressure by the pump goes to 0. The truck was still running on 0 pressure. To confirm his gauge, I saw 0 pressure by the FPR.

We started checking for power at the pump. He disconnects the connector by the pump and checks for voltage.....nothing. Yes, the truck is still running, don't ask me how. We go under the hood and check the relay. There was no power on the load side of the relay. Then check for voltage on control/coil side of the relay...nothing.

I have a Standard Ignition NO/NC oil pressure switch installed by the oil filter head. The NC side is connected to the little wire on the starter relay. The NO is connected to the former fuel heater wire. The common goes to the coil of the relay. He wiggles the terminals on oil pressure switch and you can see the fuel pressure jumping. Bad oil pressure switch.

I jump out the oil pressure switch. The fuel heater wire (IGN power) is now connected directly to the coil of the relay. Motor sounds smoother. Checked the fuel pressure gauges, by the pump it was 85 and up by the FPR was 80; more like it. I backed the FP down to 65.

What has me stumped, the motor was running without the pump. If I didn't see it with my own eyes, I would never have believed it. There was 0 pressure and the pump disconnected. Was it running on vacuum?

Probably get rid of the oil pressure switch and go with an enertia switch from a Crown Vic.

Billy T.
[email protected]

a motor is essentially a pump.. I dont know how easily it would happen but I guess it could run for a lil while..

live life full throttle

JD3020 · Sep 12, 2014

7.3 injectors will pull fuel from the tank themselves, without the help of a fuel pump. I've been around a couple OBS's with completely dead fuel pumps, mine included, that still ran and drove somewhat. Check fuel pressure and its at 0. Not good on injectors though.

co04cobra · Sep 12, 2014

JD3020 said:
7.3 injectors will pull fuel from the tank themselves, without the help of a fuel pump. I've been around a couple OBS's with completely dead fuel pumps, mine included, that still ran and drove somewhat. Check fuel pressure and its at 0. Not good on injectors though.

Yep. I've had that happen a few times too. It causes some odd things and is sometimes hard to track down.

I had a low oil pressure switch go bad on my 97 and shut my truck off going up the side of a mountain (I can't go anywhere without having to cross one). It was quite fun drifting backwards, in the wrong lane, while watching the big rig and tour bus I had just passed in the pull out lane go flying back past me, they gave me some real funny looks. :shrug:

I bypassed it and forgot about it.

JD3020 · Sep 13, 2014

I have my pump wired into the trailer battery charge relay, factory 30 amp relay on the side of the fuse block. Constant key on power, no sensors or switches to crap out and leave me stranded, and impossible to tell its there.

gnxtc2 · Sep 13, 2014

After thinking of this more, it would not matter if a inertia or oil pressure switch is installed. The motor will still run even with the fuel pump off, the injectors are self sustaining/priming.

Does anyone know if the fuel heater wire could run the pump directly? I can't use the trailer charge wire because I use that wire to charge my battery on the trailer.

Billy T.
[email protected]

Arisley · Sep 13, 2014

I have a board I built. I run the factory wiring to two relays. I have a direct battery feed off the under hood fuse box running through two fuses through the relays to my two stock Superduty pumps.

gnxtc2 · Sep 13, 2014

Arisley said:
I have a board I built. I run the factory wiring to two relays. I have a direct battery feed off the under hood fuse box running through two fuses through the relays to my two stock Superduty pumps.

Yep....I run one of these relay boards on my race car for the Weldon fuel pump. I split the FP load between 2 relays.

http://www.leashelectronics.com/Dual-70-Amp-Relay-Board-D70RB.htm

Billy T.
[email protected]