elvee

Hey folks, hoping for some guidance on what to look at next. Background on the problem: While driving the truck two weeks ago, it suddenly started bucking and surging like it was running out of fuel. I pulled into a parking lot and noticed by fuel pressure gauge was at zero. I shut the truck down, waited for a minute, and tried to restart it. The truck refired and and I had normal fuel pressure - about 17psi. Decided to go home as quickly as possible, which was only two miles away. Along the way the truck started to act up again. If I took my foot off the throttle the truck would idle fine. It only acted up while stepping on the pedal.

The truck has an Airdog FRRP pump that has been on for less than two years, and only about 15000 miles.

I started to trouble shoot by checking connections, grounds, etc. Everything clean. If I bump the key the pump runs for the usual 25 to 30 seconds. I changed the fuel filter in hopes that it was a clog from a new tank of fuel. The truck starts and idles fine.

I tapped the back of the lift pump connector so I could check voltage. When I start the truck I am showing full voltage at the pump. I can start driving it and have no problems. After about 5 minutes of driving time it just loses voltage to the pump and the fuel pressure gauge goes to zero. When it did it to me today during a test drive it did not buck and surge, but I also did my best to not give it much pedal.

So, where to look next? Wiring? ECM? Something else? Is it worth hot wiring the pump, and just monitoring the voltage at the connector?

Elmer

Sea:\>Drive

ECM controls the voltage but puts it through a relay I do believe. But usually once a relay kicks over it doesn't shut off (typical relay fail would not come on at all). Swap some relays first, it is free.

Crallscars

I recently had a relay problem, the contacts get pitted & corroded. To prove its a relay swap it with a different relay, I swapped it with my fog light relay. If it fixes it, go buy a new relay. If I remember correctly it also provides 12Volts to the VP44

dkenny

while swapping relays is easy..

I was looking at the wiring diagrams..
the fuel relay in the PDC is controlled by the VP44 or power the VP44. put another way not involved with the lift pump.

the ECM drives the lift pump direct..no relay

ref 8W-30-34 in the 2001 manual

ok so it might not be a relay..
have you tried bypassing the AD fuel pump relay.I think this the yellow to red wires..this will cause the pump to run all the time..ALL THE TIME..even after the key is turned off..

-dkenny

elvee

From everything I have read, you are right. I haven't run a hotwire to the pump yet, but it's on the list. The question is what is causing the voltage to cut out? Has anyone seen this problem and fixed it with an ECM, or was it a wiring issue? Need to pull the ECM connector next and meter things out I guess.

Sea:\>Drive

With no relay in place then I'd suspect wiring or corrosion in a connection somewhere. These 2nd gens are getting older and age can take its toll.

nascar mark

Common problem. Just bypass the ecm/pcm wiring completely and use a strong keyed source for triggering your relay of the Airdog.

elvee

If it is a common problem, what is the cause? I hate patching around a problem without addressing the underlying issue. When one thing goes out it is often a sign of what is to come. I would rather address the problem now before it becomes somthing much bigger.

jeeper50

My 2000 CTD left me sitting on the side of the road today, I suspected the truck was running out of fuel. Engine died and I tried to start it while waiting for the wrecker. Got it towed home, opened the fuel filter drain and bumped the starter to see if the lift pump was bad. It began pumping out fuel into my catch drum, cycled it again then bled the system and started the truck up. Seems to be operating normally was showing a bit over a 1/4 tank no fuel light yet. Checked codes and it shows a PO230 Fuel Pump Primary Circuit DTC active.

Sounds like its getting more common. Now what?

BigIron70

Are you running the Fass pump by a relay? If not I would suggest you do that first with a inline 15 amp fuse from battery positive terminal to power your pump.

jeeper50

Any updates? My test drive is tomorrow when I go to work, acted fine over the weekend after bleeding it and firing it up drove about 30minutes no issue yet I am running a Faass DRP Installed about 3 yrs ago.

johnh

put some fuel in it! the in tank fuel sender is bad !!! i ran out of fuel with the gage showing 3/8 of a tank.....

jeeper50

That's what I was thinking, I filled it up the next day after letting it sit overnight, put in 33 gallons in a 35 gal tank. Been driving it for several days with the full tank and will not trust the sender below 1/2 tank until I lift the bed to access the sender unit, no problems so far with it dying again.

PaulDaisy

I think the ECM backs off the voltage to the lift pump under normal driving conditions. If running an aftermarket LP, the ECM may be unable to provide the amperage needed to drive the larger pump.
My solution to this was to drive the LP from a fuse box's Power on Run wire. This also kills the LP during cranking, which helps with hard hot starts that may occur if the LP is run off a Power on Ignition circuit. Further, I am running the LP using a relay driven from the P on Run, not directly from the fuse box.