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When I first got the car running, the fuel pump would sometimes randomly not turn on. I bought a new one and improved the grounding. It has grounds going to the tank and frame now. This lasted 1 year with no issues.
2 weeks ago I did a 7 hour road trip. No issues during the drive. Stopped at the hotel to drop off things. Got back in the car to go get dinner. Came out from dinner and it wouldn't start. No fuel pump turning on. I was stranded, so I had it towed to a local shop. They confirmed that the fuel pump was dead and believed that maybe it was overheating when the fuel tank was ran low. I drove it several times for the next couple days and then did the 7 hour drive back, no issues. I have not let the fuel tank run below half full.
I drove it back and fourth to work every day this week (1 hour each way) and had no issues. Then Friday evening, I go out to start it and the pump won't turn on.
I used a voltmeter to test the connections at the fuel pump relay. Ground at the relay seems good, I don't have an inline fuse between this relay and the pump, which seems like a decent idea.
This may or may not be related, but I notice that the "key on" terminals in the other relays held a constant 4.5v, when the key was off.
Additionally, I noticed voltage drop when my electric fans turn on last time I drove it. It dropped from 13V, down to ~5 or 7V and then back up to 13V when turning the fans on. May be irrelevant, but figured I'd mention it.
Below is the LT1Swap diagram for my wiring. It's possible the fuseblocks have nothing to do with this and maybe it's more related to the sending unit, but opening the hood is a lot less work than dropping the tank, so I figured I'd start there.
Open to any suggestions on how to further trouble shoot this issue...
***UPDATE: I measured voltage at the tank and it was at zero. I swapped the fuel pump relay out for another relay and it fired right up. Not entirely confident with these results. I might run a larger gauge wire and add an inline fuse at the least....
Check the voltage at the fuel pump while its running. May be the wire is too small for the amp draw.
I agree...
That fuel pump feed wire looks to small compared to the wire coming from the battery. Nothing fries pumps faster than having wires that have to much resistance, It will cause them to overheat and shorten their life span considerably.
Volt drop testing is a must.
I'd go as far as questioning the integrity of the connections thru the bulkhead.
I'd pull the pump, and see if the in tank connections are fried.
As the volts go down, the amp draw goes up.
A clamp on amp meter is a big help.
I'd also isolate the pump circuit, and make it a "stand alone" deal.
Where is the batt located?
You got good advice above. Low voltage at the pump will kill the pump fairly quickly. Ideally, you want over 13V at the pump while it is running. Also make sure you have a genuine Walbro pump and not a counterfeit.
What Andrew said!
"Also make sure you have a genuine Walbro pump and not a counterfeit". We had a rash of that in the turbo Buick community. Nasty stuff, when a boosted engine gets no fuel....
What Andrew said!
"Also make sure you have a genuine Walbro pump and not a counterfeit". We had a rash of that in the turbo Buick community. Nasty stuff, when a boosted engine gets no fuel....
+1
Buy the Walbro pump from a reputable source. The first one I bought was some internet source (don't recall the name), and it failed after little use. The replacement from Summit is still working, years later.
You have great advice here, but thought I'd add a little.
I don't know your EFI tank specifically. Does that mean it has an extra fitting for the return or that the pump is inside the tank?
If not inside, is the pump mounted equal to or lower than the bottom of the tank? If not, this could be the issue. The pumps are supposed to be gravity fed, not suck from below. That can stress and destroy the pump, too.
I use a voltage drop calculator like this one when determining wire size on critical wiring. https://www.calculator.net/voltage-drop-calculator.html
Estimate the pump current as 7 to 10 amps. Aim for a drop of .5V or less, given your history, I might even oversize to loss of around .25V or less. Don't forget the length of the ground.
It might be good to separate the fuel pump relay feed from the fuse panel, so it isn't as affected by electrical spikes caused by high draws like the fan and additional voltage drop by undersized main feed wiring. (voltage drops are additive for wiring which is in series) You could run a separate and local relay to the pump (if exposed use a sealed one like for a marine application and feed from the starter lug or battery.)
I measured the voltage and amperage at a quick connector I have roughly 1' from the pump.
I went ahead and replaced all the relays and 15A fuses. Looking at the wire running from the relay to the fuel pump, it looks pretty robust. Maybe 12awg? This connects to the gray wire shown in the below photo. Might also be possible that the wiring in the sending unit is bad... I've just hesitated dropping the tank again.
Here's the quick connector running the wire from the relay back to the sending unit. Here's my voltage reading Here's my amperage reading
When I wire them,,, its 10G for supply and ground and the ground gets a
dedicated wire back to the Battery negative. Frame grounds have been the source of more
DNF issues on road race cars that I've crewed for than just about any other cause..
A dedicated brass ground bar on the firewall with a 8 or bigger wire to the main battery ground cable
is the other half of my typical shot at it..
Counter fit Walbro pumps are way too common.. sadly..
Dead heading the pump is often the problem as well, I try
to pick the regulator able to pass at least 50% of the pump
volume if needed,
the outlet/return side should have virtually no pressure.
One of the reasons I never use a single ended fuel feeds,
The local loopback pressure relief allows heat buildup and cavitation in some cases..
At least in road racing,, I'm sure the profile is different for drag racing.
I had a similar problem. It ended up being the short connector from the pump to the sender base. The connector at the base had melted nearly in half. Swapped out the sender and upgraded to an Aeromotive Stealth pump. Problem solved.
Not a lot of update here... I haven't been driving it out of fear of it dying on me. It seems underpowered at idle and my electric fans stopped turning on for some reason. When I turn on the headlights or interior fan, I notice more of a drop in power than I'd seen previously. You can hear the hum of the fuel pump for example change tone when turning either on, and then it goes back.
I measured the battery with the car running and off.. It seems like the battery and alternator are good. I noticed I have a soldered section extending the wire that goes to the pump. I might just replace it with a new 10AWG wire for safe measure.
I might end up dropping the tank this weekend to take a look at the sending unit. Part of me wants to just redo that whole fuse block, but I'm moving out of state in a month and will at least need the vehicle to power on to get on a transporter. Rather not get stuck with a vehicle that won't start. I'll keep yall posted if I find anything. Appreciate the help!
I have a tendency to over-think, but here's another thing that I've never felt to sure about....
I have my main power to the relay block coming from the starter post in this picture. The yellow arrow shows the wire that goes to the fuse/relay marked "12V+ BATTERY" The red arrow is the wire that goes to the battery itself. They share a post, which maybe doesn't matter?
And this is the positive side of my battery. The red arrow is the wire that goes to the starter. The blue arrow is a wire that I have going to my relay for my fans.
Reading the post before last, it sounds like that you have some voltage drop issues. As various devices are activated, other devices begin to suffer. I don't see any obvious issues with the pictures above, but it's not always easy to judge the quality of the connectors.
If you are hearing the pump noise change, I suspect that is because the voltage it is getting has changed. Have you checked voltage at the pump when other devices are turned on?
One sure way to fix this is to run a ground and power wire directly from the battery, back to the tank. Ground the negative directly to the pump. Install the fuel pump relay in the back and run the trigger wire along with the power and ground, back to the relay.
Reading the post before last, it sounds like that you have some voltage drop issues. As various devices are activated, other devices begin to suffer. I don't see any obvious issues with the pictures above, but it's not always easy to judge the quality of the connectors.
If you are hearing the pump noise change, I suspect that is because the voltage it is getting has changed. Have you checked voltage at the pump when other devices are turned on?
One sure way to fix this is to run a ground and power wire directly from the battery, back to the tank. Ground the negative directly to the pump. Install the fuel pump relay in the back and run the trigger wire along with the power and ground, back to the relay.
Andrew
I like this idea and I can't see how it would not fix my problem. Went ahead and ordered 2X10' 10awg for the ground and battery positive along with an inline fuse to add near the tank.
Also like the turbo idea. Who cares if it runs? It's gonna look sick on the internet with a turbo haha.
Removed my tank today. It was nearly full but super easy to remove with a transmission jack.
I've ordered qty 2 20' lines of 10AWG wire for ground and power directly to the battery, a waterproof relay to go underneath the truck and near the tank and a waterproof inline fuse holder. As shown below the wires that came on the sending unit are 18AWG, I believe the same goes fro the ones inside the tank, but I haven't removed the unit yet.
If I were to update those to 10AWG, it seems like it'd be a lot higher risk situation than I may be comfortable with... never done it though and not sure how necessary it is. Isn't it Ohms law that would mean regardless of running 10' of 10AWG, if the last 1' is 18AWG, I'm no better off than running the whole thing with 18AWG? I could be off on that...
Oh and I looked at the receipt from the shop that replaced my fuel pump when I broke down during my road trip. The pump they replaced it with is not a Walbro 255. It's this "Precision Fuel Pump E16030". No idea how good it is, but it's definitely loud as **** and retails at $60 from O'Reilly which is a little bit of a red flag... https://www.oreillyauto.com/detail/b...e16030/4615455
These are the wires coming directly from the bulkhead of the sending unit. They original all 3 went to a weatherpack connector, which I cut off and instead ran them individually. All three are 18AWG and 1-2' in length. The 12V goes to a 10AWG that's about 4' long. I soldered it to what I believe is a 12 or 14 awg (it's unmarked) that covers the remaining 6'..... not proud of this, but I seemed to have think it was a good idea at the time
Ground wire towards the right goes directly from the sending unit to the frame. I then have 2 additional ground wires, grounding the tank. Second grounding wire that just from tank to frame. Sending unit bulkhead connector Another view showing fuel lines. 2 outside lines are fuel and return, middle is vent which just hangs over my rear end.
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Fuel Pump Keeps Frying 
