2005 F250 losing prime

[Kimsboat]

Been chasing my tail.....2005 F250 loses prime after sitting. Engine runs perfect idles at 600 maxes out at 6000 and perfect in between. My problem is that I have to prime the bulb if we sit shut down. It will start fine but runs out of fuel shortly after, pump the ball and it will run great until the next cycle. I have replaced the spin on yamaha 10 micron filter before the motor, the filter in the spin on cap at the front of the motor,the filter inside the VST tank, the F filter and the high pressure pump inside the VST tank and the inline check valve. Cleaned the tank while off(it was really clean inside to begin with).
What am I missing from what I can tell the only thing left is the low pressure pump and the primer ball?

Help-Thank

[99yam40]

check for plugged fuel cooling line.
VST may be heating up and boiling the fuel out.

but also need to make sure the lift pump comes on when it should when problem shows up

[fairdeal]

well, you have certainly replaced plenty of parts.

The VST holds about 8 ounces of fuel.
At idle, the engine uses about 0.6 gals/hour - thats ~80 ounces per hour
So if your VST is full when you shut off the engine -
when you restart it has enough fuel to idle for 1/10th of an hour - 6 minutes

the lift pump runs as soon as the engine starts -
and I've read, but haven't tested it, that it initially runs continuously for several minutes.
After that, below 1200 rpms, 10 seconds on, 20 off
Even at 10 seconds on, out of 30 seconds there is plenty of time to re-fill the VST...

Interesting that there is no complaint of hot restart difficulty -
one might expect flooding after boiling off the VST contents

I'm leaning toward a restriction - or an air leak - on the lift pump supply
although the problem with that, is it runs fines up to 6000 rpms...

It would be very interesting to know:
what is seen if the bulb is pumped immediately at shutdown -
does the VST take fuel then? or not

[Kimsboat]

Thanks for bashing your brains with me.

Yesterday I came home fired it up on the hose and it died within minutes.....no more than 5.

Pumped the ball ran fine. Waited an hour started up without and ran for 15 minutes on the hose no issue?

[fairdeal]

in your shoes, i would do some testing on the lift pump

it always has power at key on,
stick a paper clip in the back side of the connector and ground it with a test lead to make it run

do you have an ordinary fuel pump vacuum/pressure gauge?
with a 5/16" Tee and some tubing:

Tee into the suction side - you should see virtually no vacuum when the pump runs

Tee into the discharge side - it should be making >5 psi while filling the VST, and max out at close to 14 psi when the VST is full

also, patch in a length of clear tubing on the suction side, and check for bubbles while running the pump (if you have any, that's an air leak somewhere)

and measure what comes out of the "full" VST - make sure the float isn't set way off

[rodbolt17]

I would look at the lift pump relief valve.
but that is just me.

[Kimsboat]

Where is that?

Im trying to post a video too....lot of air being passed threw the lines.

[fairdeal]

I would look at the lift pump relief valve.
but that is just me.

except you missed, in that laundry list of parts thrown:

I have replaced .... and the inline check valve.

[rodbolt17]

I really don't care what was replaced. was it tested for proper operation?
that pump below 1200 RPM runs 10 sec on 20 sec off.
any air leaks or the relief valve leaks results in fuel starvation and low speed shut down.
can be simply observed by watching the fuel level in the cup.

[Kimsboat]

That is for sure I have thrown the kitchen sink at it!

I have more than a little air. I installed the clear tube as suggested and watched. Key on ----No movement of fuel. Started the engine and the pump kicked on and off every 20-30 seconds. Lot of air and actually ends up sucking the filter housing dry. Then in between cycles fuel starts to bubble back towards the cup filter till the pump kicks back on and a wisp of fuel air is pushed threw. Revved up to 1300 and the clear tube was dry --no fuel.

[oldmako69]

Kimsboat,

Welcome to my world. I have a pair of 2005 F225's and have had a similar issue since day of purchase (August of last year). At first it only affected No 1. I changed and checked most of the same things that you did. All to no avail.

I checked every inch of the fuel delivery and filtration. Everything was spotless and showed zero contamination. No cracks in fuel lines ends, loose clamps etc.
I replaced the squeeze bulbs with new from Yamaha.
I swapped out the inline check valves from one side to the other.
I pulled and cleaned the VST. When I did, I found evidence of gasket compound on the VST lid (which is not to be used) AND small bends all around the base of the HI-PSI pump as though someone had attempted to pry it open. Now bear in mind that these engines only had 125 hours on them! So, clearly this engine had been a problem child all along.

Eventually, the engine would not start at all even though the VST was full and the spark was fine.

I figured that the Hi-PSI pump within the VST had failed due to it running dry so many times. I replaced BOTH the hi and low PSI pumps and the engine has behaved flawlessly ever since. Admittedly that is only about 35 hours or so, but I'LL TAKE IT!

Now, the same symptoms are present on Eng No 2.

I read a thread on a different board written by an ASE trained auto mechanic who had similar issues with both of his engines. He ended up replacing both engines Low PSI pumps to solve it. Now he hasn't been to Yam school, but he clearly ought to know more than I when it comes to troubleshooting a modern gasoline engine's fuel and electrical systems.

Here's the problem as I see it, I can remove the cowling on my engine and put a finger on the low psi pump to confirm its operation (10 on 20 off). I can also watch the first stage filter quantity ebb and flow in response to the low pressure pump, yet sometimes the engine will still fail with fuel in that first stage and the pump running. Its got fuel. IF I have someone on the boat who can drive, if I run back and squeeze the bulb firm again the instant it starts to shut down, then I can prevent it from stopping. Sometimes.

It also seems the worst when the engine is the hottest. If you run it for a bit, then shut it down the whole mess gets heat soaked. If you then start it up and try and idle for a bit, it will usually die right away. All this is very frustrating.

Best of luck to you.

[99yam40]

need to find the air leak.
might move the clear tubing to different places to help figure out where the air is coming from if you cannot easily find it

[Kimsboat]

put it on a remote tank and problem solved?!?! clear tube stays full with fuel.

Two things in the way screw on filter (maybe housing bad) or the pick up in the tank?

Replaced primer bulb yesterday and hoses.

[fairdeal]

[QUOTE=Kimsboat;141203

Two things in the way screw on filter (maybe housing bad).[/QUOTE]

good to hear you've narrowed it down.

Several possibilities with the filter;
loosely threaded fitting
split hose at barb
corroded gasket surface
just to name a few

IIIRC Rodbolt has encountered a filter head with the unused port not plugged

[Kimsboat]

Man this is getting frustrating.

Pulled the ASV and pushed the ball and spring out thinking that was a possibility. While there inspected the pickup tube. Seemed to be fine no cracks, splits etc. Also no screen on the end? Tank is 3 years old.

Hook it all back up(port motor port tank) and eventually the pump pulls the cap filter dry and starts pulling air. Swap over to alternate tank (Starboard tank -Port Motor)and the hoses stay full with the cap refilling after pump kicks on and off.
Put starboard motor on suspect tank(port) and you guessed it same thing emptied the filter hosing dry and began to pull air.

What the heck am i missing. Remember this all started because at idle (port motor-Port Tank) it would periodically shut off and i would have to pump the ball. Once primed will run all day from idle to 6k. If it was a fuel starve problem caused by the tank wouldn't it act the same at idle verse at cruise or WOT. I ran 25 miles at 4400-4600 rpm after pumping the ball with no issues.
Help-Red Snapper season just re opened!!!!