In last thread I was working on a jag for a freinds shop and had all sorts of fuel pump issues. Main being he was sent generic universal pumps and they had a hard time working with the current system. Led me to checkin up on my own.

I replaced both my pumps a few months ago with Airtex. I checked today and both pump relays were hot. I was not really using the second so its got me a bit concerned. Considering it is both relays that would lead me to believe something shared causing this. Ground and possibly jammed fuel line....

Question is what is easiest way to add or fix a ground to the harness outside the fuel tank. Can I/should I splice into the wires just outside of harness and somehow screw them into frame right there. Would that be a sufficient ground. What if I added a second wire out of harness and grounded that additionally somewhere?

Any help on this is appreciated. After this I'm looking towards fuel line and injectors.

 

Not a fan of Airtex, I went through 2 of them on my Expedition before I got one to work after my OEM had died after 400k.
Heat is generally from an improper or worn application, thus it can be an improper wire gauge, say using 16 instead of 14 (very common Chinese manufacturing on a house vacuum. Run a vacuum for awhile and feel the wire and how warm it is, it slowly kills the motor).
Many things need to be considered, number 1 is distance, then amps, then voltage and what's the requirements of what you are energizing. Most any auto application, other than its primary power lead, will use 18 gauge. Ohms Law states the reason for a "hot lead" to be resistance. Thus a receiving source not getting enough power and trying to draw more than the provider can give...either it be from too small a wire, shorted wire or poor ground. A shorted wire can simply be a poor connection at your connector....the spades or incorrect type of wire or poor soldering or a relay. If your connector (shield) is cracked or too thin for shielding, the voltage could be jumping (shorting) to the other connections and making it hot (Chinese, Taiwanese products). If there is a short, the amount of power being able to be drawn is limited. You shouldn't have to add a ground, the appropriate application was already done when it was built. It may need attention, but you shouldn't be needing to add one. If your ground was bad, it would be warm.
I would check your relays, the contacts may be scored and need replacement? With the new pumps, your probably pulling more power than the old ones because they're new and now the relays are the next weak point. They could have gotten scored from the old pumps going bad? Its also a lot easier work and most likely needs to be done anyways after all the years of use.

 

took a while to get back to this. Both pumps are now Airtex but bought couple months apart.

Pump 1 is pulling 8 amps
Pump 2 is pulling 4 amps

This was measured around idle. I know these types of relays can get warm but these get pretty hot.
Everything else seems to work fine. There may be a bypass-valve issue but working on that.

I still have not tested fuel pressure yet with gauge but based on fuel trims it doesnt seem to be starving at any point.

Those amps seem correct? Should second pump relay have power at idle?

 

Its my understanding that pump 2 is activated when the SC is pushing more air than fuel and thus the ECM activates it. As for constant power, I cannot answer that, I have not been into mine that much. Perhaps motorcarman or someone like that could answer it? ...I'd try PM'ing him.

 

Col,
When my 99 XJR came to me one of the pumps was not functioning. I checked the relays and fuses 1st just in case and found a non-stock ground pigtail. I pulled it and the tank and replaced the pumps only to find out the car wouldn't run without the extra pigtail.
I knew that wasn't right so I pulled the 2 relays and flashed new solder on all the lugs. I plugged them back in and everything worked fine (so far). I'll check the relays for temp when they get to my driveway tonight but High Horse has a good point. Any resistance in the path can generate heat. You can get resistance just due to low normal force at the mechanical contact connections (low force, crud, oxidation, etc). I don't know how many amps your pumps (or mine) should pull and the resistance could be coming at any of the other connections, outside or inside the tank but it's pretty easy to pull the relays and tin the lugs with a little solder to see if that's where the issue is.
It will be the 1st place I look when I chase my next electrical issue...

 

Pump 1 is pulling 7 amps
Pump 2 is pulling 4 amps
I did not check it and forgot to ask what the method was (running, idle, startup, etc)
Page 67 of Engine Management manual says 7 amps at 13.2V at 3 bar (43.5 psi)

I do know with the style of relay there will always be some resistance and heat. The magnetic/mechanical contact will cause some.

When you say "tin the lugs" are you referring to the relay, or adding solder to the female in the fuse box?

I think it is in box somewhere cause both get warm even if secondary was not running.

 

Col,
Sorry for the delay, I was trying to catch the last night of the super moon.
The relays were warm when the little woman pulled into the driveway. I can't say one was cooler than the other but they were warmer than room temp (it was 60 F here at 5:00 PM). She babies the XJR so I'm not sure if the second pump was even working on her trip home.
When I say tinning the spades I used the iron to heat the male spade on the bottom of the relays and then held the solder about 1/16" (1 - 2 mm) away and flashed some solder on, no big blobs just a somewhat uniform coating. You can always go over the spade with the iron to drag some off if it looks too heavy. Probably amounts to less than .005". I suspect the female connectors in the box may have relaxed in the years since they left the factory and contact resistance is very dependent on contact normal force so this is just a quick way to increase normal force. Solder is pretty soft compared to the terminal brass so it probably gets displaced. I haven't puled either relay to check that but it allowed me to recycle the non-stock pigtail to ground someone thought this old girl needed.

 

^^^Thanks. That is what I figured you meant. I'll try that and see what happens.