5.0 GXi-J fuel pump relay keeps tripping

[kevinmongar]

Yes the fuel pump fuse is a 20A.
I was just pointing out that the empty relay connector area (where the old relay was removed), with wires cut from the bottom of the box, still got to about 120 degrees...and that this now empty/unwired area happens to be next to the 40 A fuse (instrument panel, M1 in pic) in the box. It just seems weird that this now open spot would get hot.

 

[alldodge]

Things are not adding up. There is no reason that the relay should get even above warm unless something else has been added to the circuit.

You say even the area next to where the 40Amp fuse is getting hot.
That being the case, need to get in behind it to see what is causing that

 

[kevinmongar]

Yes I agree..."Things are not adding up".
1. New fuel pump relay; It was just 'warm' to the touch...but when I use this infrared/laser temp gauge and move it around the top it gradually got up to 130 degrees but only at one spot (where my finger nail is in the pic; it is on the side that the purple wire comes in). The sides and bottom were about 90 degrees. Regardless, I have a feeling that just moving it out of the fuse box should help with the relay tripping problem.

2. Hot spot in box; Seems like the box itself was part of the problem as a heat source; It looked fine in that area from underneath...but it is very hard to see up inside. You can see on the pic where it got the hottest when the old fuel pump relay was in there (that is around pin 30/red/yellow on the old relay). That is where it is still getting up to about 120 degrees. (And the wires to that old relay are cut off below.) The 40 A fuse next to it is not hot (the fuse prongs are not burned at all). The relay above that area is not hot. The relay below it (ignition) got up to about 105 degrees (maybe because it is next to the hot spot?)

It has me scratching my head.
Again thanks for the help/advice.

 

[alldodge]

Wish I had something to offer, but like you I'm lost to what could be causing it

I might be thinking about opening the box with a dremel to look inside

Or start following wires out to see if they are also getting hot and where ever they go is also

 

[Grub54891]

Could the fuel pump itself be starting to go south causing it to draw too many amps?

 

[ESGWheel]

I am going to offer some advice that you may not like but I am doing so out of concern for your safety. The temps and symptoms you are experiencing are dangerous as in electrical fire dangerous. Hopefully, it is something simple like an over drawing fuel pump. My strong advice is to not take this boat out until this issue is resolved.

There are two approaches to this: find the issue yourself or take it in. If you are comfortable with taking on this sort of challenge and willing to spend some bucks on the needed tools, I have no doubt you can troubleshoot it with some patience and using this forum.

For tools, one is to trace where those wires go. As you know even with a wiring diagram it is hard to trace out a specific wire in all the wiring looms. One method of tracing a wire is using a tone tool, like this link. Simply following the power wires to/from the relay may lead to an obvious visual issue like chafing of the loom where it has got some sort of short. Barring no obvious indications while tracing the wires, then a more expensive tool to trace out a short like this (link) one is in order. See this instructional video on how to use it link.

And there are other ways to tackle this issue, like judicious use of a Multimeter.

Again, please resolve this issue as a priority and do not get underway until it is.

 

[kevinmongar]

OK thanks for the advice. I don't plan on taking it out until I get the heat problem in the fuse box resolved. So far I have not found any 'parasitic draw' or shorts.
Does anyone know what the normal current draw for the fuel pump should be? The place I bought it from did not know.

 

[ESGWheel]

While I have never measured it, since its on a 20A fuse, the combined pumps probably draw somewhere around 12 to 14 amps. I am about to de-winterize my boat and can measure it if still in question.

 

[ESGWheel]

Here is another thought and an old school way to find shorts (or other high current draw devices, ie exceeding what they should) while minimizing risk of further damage: use a flasher relay. It’s been decades since I have done this but I do recall having one of the guys show me to hook up a flasher relay in place of the fuse that keeps blowing. What happens is that the flasher will open circuit based on the current draw, and then cool down and close, repeat, just like your turn signals. With the on / off again of the current it reduces the risk of burning up the wires. Then take a DC Amp induction meter and start moving it along the loom / cable looking for where getting a large deflection and then a much smaller one. Like using a stud finder go back and forth and you narrow down the area of interest. I looked for DC Amp induction meters and while I found some cheaper ones overseas, here is what seems to be available in the US and its not cheap link.
Keep poking and good luck!

 

[kevinmongar]

OK thanks. I am still working on it and have ordered a good clamp amp meter. I still have not found any spec for normal fuel pump current draw. If you could measure on yours it would be greatly appreciated. I used Chatbt and it said normal was about 10 amps...but who knows.

 

[ESGWheel]

I have been delayed de-winterizing my boat due to medical issues. I hope to get to it in the next couple of weeks…

 

[Lou C]

The amp clamp is a very useful tool to have, the thing you want to think about is not just how many amps the fuel pump draws, but also how many amps the wire is rated for. With fuses and circuit breakers the rating is chosen to protect the wire from overheating and causing a fire. Not sure where you could get amp draw specs for the pump, but if what you measure is close to the limit of the wire gauge in the circuit, and the wiring is getting hot, then we can assume that either there is some other source of resistance in the circuit or the pump itself is drawing too much current. That many not mean the pump is bad, there are fuel system restrictions that can cause that too, such as a clogged or rusted anti siphon valve on the fuel tank. What is the rating of the circuit breaker or fuse for the fuel pump, that's a good guide right there (just checked your pix, I see it's a 20 amp fuse, it would be interesting to see what you find with the amp clamp).
One thing I like about the older small block and inline engines, that lovely device of the distant past, the mechanical fuel pump. Simple and works for decades, no wiring or relay headaches, and cheap to replace.

 

[ejnichol]

Did you try unplugging the two pumps and then switch ign key on? Did heat go away after having them eliminated from load.

I assume your getting this heat when engine is running? Pumps should pump up at key on and then shut off at some time or pressure threshold.