F200 blowing 5 amp fuel pump fuse on cold starts

[wiznut86]

It seems that my one time fluke has become a regular problem. 2004 F200TXRC. The 5 amp fuse for the low pressure lift pump keeps blowing on cold starts. After replacing each time, it will run all day long with multiple stops and restarts without a single issue. Then the next fishing trip on a true cold start, it will blow again. This has happened three trips in a row now with it blowing first thing in the morning and then after replacement will run and restart fine all day long. I have no idea where to start with this

[Sequoiha]

A bad lift pump, try a 7.5 amp fuse and see what happens.

[99yam40]

after installing a larger fuse, I would try monitoring the amps being drawn cold and warmed up to see how much the pump pulls. if the pump is what is pulling too many amps when cold,I would replace it

[wiznut86]

Will give the 7.5 amp fuse a shot and see what the amp draw is at cold and hot starts. That darn little pump is expensive!

[Sequoiha]

Yes it is.

[wiznut86]

Tried a 7.5 amp fuse and it held without a problem on cold start. Need to get my electrical engineer friend over with his fancy multi meter to get an exact measure on the amps it's drawing. Based on just what I've experienced with the fuses, it looks like it's pulling just over 5 amps, but under 7.5 for just a few seconds or less at cold start, and then pulling less than 5 amps the rest of the day on warm restarts.

Then the question is.... if it's drawing just barely over 5 amps for such a short time, is there going to be any large risk to the wiring or burning the boat down by just running the 7.5amp fuse?

[zenoahphobic]

Tried a 7.5 amp fuse and it held without a problem on cold start. Need to get my electrical engineer friend over with his fancy multi meter to get an exact measure on the amps it's drawing. Based on just what I've experienced with the fuses, it looks like it's pulling just over 5 amps, but under 7.5 for just a few seconds or less at cold start, and then pulling less than 5 amps the rest of the day on warm restarts.

Then the question is.... if it's drawing just barely over 5 amps for such a short time, is there going to be any large risk to the wiring or burning the boat down by just running the 7.5amp fuse?

Probably no risk to wiring using 7.5 Amp fuse, however the 5 Amp fuse should have been adequate, if that is the value intended by the manufacturer.
I would check that first (someone can look this up) and the current draw specified.
If that is correct your pump motor has extra load, most likely the bearings I.e. lubrication, water ingress (rust) or some other seizure, that loosen up when warm.

[pstephens46]

Oldmako- what is the l/p aftermarket pump you are using?

[Sequoiha]

Probably no risk to wiring using 7.5 Amp fuse, however the 5 Amp fuse should have been adequate, if that is the value intended by the manufacturer.
I would check that first (someone can look this up) and the current draw specified.
If that is correct your pump motor has extra load, most likely the bearings I.e. lubrication, water ingress (rust) or some other seizure, that loosen up when warm.

Like I said in my first post, bad lift pump, I replace them quite regularly.

[TownsendsFJR1300]

Like I said in my first post, bad lift pump, I replace them quite regularly.

It's now obvious that's the problem. Boating isn't cheap.

I wouldn't be gambling with burning up an entire engine (or getting stuck eventually) with a known bad / failing part. It's the price of ONE tow..

Replace it and be done with it..

Just my 2cts..


.

[wiznut86]

Thanks guys. I guess it's time to bite the bullet and buy a new pump. Appreciate the kick in the pants to get me to do it!

[boscoe99]

What exactly is provided power through the 5 amp fuse? Seems to be the LP pump and the pump driver. What if it is the driver that is causing the excess current flow?

Has fairdeal ever ohm'd his motor out to know for sure? Has fairdeal ever used an ammeter to measure current flow through the 5 amp fuse?

Fuses are generally sized to protect the wiring. I suspect that the wire size to and from the 5 amp fuse is rated for at least a 10 amp fuse.

[wiznut86]

What exactly is provided power through the 5 amp fuse? Seems to be the LP pump and the pump driver. What if it is the driver that is causing the excess current flow?

Has fairdeal ever ohm'd his motor out to know for sure? Has fairdeal ever used an ammeter to measure current flow through the 5 amp fuse?

Fuses are generally sized to protect the wiring. I suspect that the wire size to and from the 5 amp fuse is rated for at least a 10 amp fuse.

Hmmmm... This is the first I've heard of a fuel pump driver. I already ordered the pump before you posted, so I suppose I'll find out for sure when it gets in and I give it a shot. Is this the driver that you're talking about?: 69J-83306-01-00

[fairdeal]

Has fairdeal ever ohm'd his motor out to know for sure? Has fairdeal ever used an ammeter to measure current flow through the 5 amp fuse?

Have not. And sadly, unlikely to get to it for a while;
I've got the boat in the water, hoping there is a weather window to get an offshore *****ing trip in
with barely enough time before I pack everything up for the annual travel for "Christmas with the in-laws in New Jersey"

[pstephens46]

Have not. And sadly, unlikely to get to it for a while;
I've got the boat in the water, hoping there is a weather window to get an offshore *****ing trip in
with barely enough time before I pack everything up for the annual travel for "Christmas with the in-laws in New Jersey"

Sounds like you are excited about this trip. I know how you feel...we have some strife in my wife's family this year. First time in about twenty years. I really want to stay home. Or maybe just go visit Boscoe in Kennesaw.