Evenin, DTR.

Doing the AD install on my buddy's 99 24V. The truck has the in tank retrofit.

I hooked everything up, the pump runs solid when I bump the starter, and has 12v, but as soon as we start cranking, voltage drops down to 2-3v. The batteries are manufactured in 06, but the truck turns over fine. I read the voltage at the battery that I have the power hooked up on when he was cranking it, it was 12v. Sorry, no FP gauge, we had one plumbed into the VP44, but the AD made us remove it.

I bled all the air out of the lines, it was dripping solid fuel at the VP44 when I was bleeding it, and got it shut before the pump cut off.


???

 

The 24 valve ECM's cut back voltage to the Lift Pump circuit while cranking. VP44 injection pumps do not like having fuel pressure coming at them while trying to start the engine. Once running, the voltage should bump back up to 12+ volts.

 

Ok...

So, what I did was... I took the plug that goes to the original lift pump power supply (the AD one) and used a couple of butt connectors to run power straight from the battery. Truck started right up. Hooked the plug from the AD back into the original LP plug, nothing.

 

You're not getting any voltage (well very little) through the OEM LP harness when the truck is running?

With the intake retro fit, are you plugging into the harness near the tank, or up at the original harness along the block. If you have proper voltage while bumping the starter, that voltage should come right back after cranking/starting. Only thing that comes to mind if it's losing voltage through that circuit once the engine is running is maybe the ECM is throwing a fit.

Are you running the truck with the AD unplugged and checking for voltage at the harness, or is the pump just not turning on once running (through the OEM LP harness)

 

Correct. When he bumps the starter, I get 12v. With the pump running, he will start cranking it, and it drops to 2-3.

I plugged into the plug where the original pump was at the FF canister, it is what AD sent me. Regardles, the wires going to the pump in the tank plug into the harness at the old plug at the FF canister.

The truck ran fine before the AD. Good FP.

I took the wire loose at the AD, that is were I was getting the voltage reading from. The pump runs when you bump the starter, or after you try to crank it, and let off the starter, but leave the key on.


We gave up for the night... if we cannot figure it out through the DTR, I am going to find a 12v hot with the key on in the IPM, and rig it like that until Monday when we can call pureflow and see what's up.

 

Bump for the am...

 

Is this the only problem that is occurring? Or is the voltage not bumping back up to 12 volts once the engine is idling?

As I mentioned earlier, the voltage will drop on the lift pump circuit when the engine is cranking over. However, once the engine is running/idling, the ECM will bump the voltage back to 12+ volts. From what you've mentioned I'm not seeing a problem, unless I'm reading your posts wrong, LOL.

 

Whats the lift pump voltage w/ECM stock wiring with the engine running?
Mine is 11.5 volts.

 

With the engine running, it's 12v.


I believe that the ECM is not putting enough voltage out to supply the AD with the power to push enough fuel to start the truck.

That's ok, I rigged it with a switch. Runs great!

 

If the truck is not starting properly, there is air/something else wrong in the system. Or his Vp may have a cracked diaphram...reason it needs the positive pressure while cranking. Or it has to bleed out all the air first then fires. WIth it wired in hot all the time, it might be enough positive pressure to clear the air out and fire like normal.

If he isn't concerned about it than run it the way it is, however it still doesn't sound right. VP's do not need pressure to start. There will be enough fuel in the lines and the VP from previous shut down. Vp44's also are able to pull their own source of fuel (about 4psi). Not good for them by any means to have negative pressure...but they can start on their own (when in good condition).

But i'm carrying on, too much reading, LOL. Keep drivin er if he's happy with it