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To start, I'll list pertinent mods: Built2Apex in-tank surge tank w/ Walboro 450LPH pumps and the Chuck Westbrook FP Re-Wire. Whole fuel system is AN-6 w/ CJM secondary rail and ID2k injectors. OE primaries.
Last week, I was tracking my FD. Fine all day Saturday. Within the first two laps on Sunday morning, it seemed like I was losing throttle here and there. RPM would go down as if the throttle cable popped, but then would come back. Within a few more turns, there was no throttle response and the car killed. I could not re-start. After getting towed off track, I checked fuses (all fine), and after awhile we eventually found that the pump that pulls from the main tank was not working. The car had sat in cold conditions with the hood up all this time. The pump that sends to the engine was working, so I pulled the surge tank body off, and drove home and ordered new pumps on Wednesday.
The pumps arrived yesterday (Sunday), and I replaced them. After replacing, The pumps prime and the car fires right up. I let it idle awhile, then take it around my neighborhood for a shakedown. About a half mile from home, the same thing happens as at the track, so I coast and pull over. No pump prime noise, and no starting. I call a friend to tow me back home, and I first think that the pump(s) may have burned-up. I tested voltage, and there is none to the pumps! That's when I take a 9V battery and test the old "broken" pump. The pumps I replaced both worked! Later that evening, after the car cooled off well, I decided to just bump the key. I did that, and the pumps primed!!
At this point, It's safe to say that: Once the car is hot, something is preventing voltage from going to the fuel pumps. I suspect it may be the EGI main relay, as my fuel pump relay was relocated when I installed my Greddy V-mount. It's now in a much cooler place in the nose with all those heat exchangers between it and the engine.
To test it, I'm planning to use a heat gun to carefully heat the EGI main relay (not sure to what temperature, but I'll start at 90F, and not exceed 120F), and testing if the pump primes. If that does it, I either melted the relay, or confirmed my problem. For posterity, I will record the outcome here.
In the meantime, I am hoping someone has experienced this same problem, and can either confirm my suspicions or have another root cause idea. I'm all ears!
I like your approach to this problem. Definitely try that. Even though you did the pump rewire, do you still have the resistor box under booster plugged in?
I like your approach to this problem. Definitely try that. Even though you did the pump rewire, do you still have the resistor box under booster plugged in?
Yes!
Update as well:
Heated the EGI relay area with a heat gun 'til the heat gun measured about 160F, but the pumps were still priming. I quickly started the car, with the hood closed, to build bay temperature. After about 15-20 minutes, I decided to drive up and down my driveway, and the voltage to the pumps killed. I got an air mattress pump, and held it on there for a bit, and it wasn't priming. I pulled the yellow EGI main relay, and threw it in the freezer for 10 minutes, and popped it back in. No dice. I then pulled the green relay, and put them both in the freezer for 15 minutes. Took them out, popped them back in, and turned on the voltmeter. priming!!
I cannot tell if it's just the yellow EGI Main Relay, or the green main relay, but the car runs. I'll put an order in w/ Ray for these, this week.
TL;DR:
EGI Main Relay or Circuit Opening Relay was causing a cut to the fuel pump voltage when car was warm. Pulled them, stuck them in the freezer for 15 minutes, and the car now starts.
If you still have the resistor under the booster, remove it. Cut the plug off it and make a jumper out of it. The red/white wire still completes the circuit through there so you have to bridge it.
I was advised, by a local FD specialist, that I should also be testing for any conditions (i.e.: overheat) that may cause the car to cut voltage to the fuel pumps. Also, some observations I have made since getting the car up and running since October of last year:
My pumps only prime for about a second or so. Not very long. I am told they should prime for longer.
Checking today, voltage to my fuel pumps is only 5.35V or so at idle. I am told that this voltage is also low. I still need to jump-out the high-speed relay and see what happens when the pumps get the full 12V. I want to see if anything else is causing the voltage cut, and I want to see at the full 12V.
I would hate to buy these expensive relays, thinking they solved the problem, and that not be the case. I will be removing the nose of the car to get to the fuel pump relay. Not my idea of a good time, but I'd rather be thorough about this. I am going to re-trace my Chuck Westbrook fuel pump wiring job, and test per the FSM and advise from the local specialist.
At this point, I'll do some more testing when things are easier to get to, and I will report back.
1 second for fuel pump prime is about right when you turn the key to On with the stock ECU or PFC.
With the fuel pump resistor relay you should see 9v at idle/low load and around 12-13 at high load. You can tap a multimeter Into the fuel pump wiring and drive around to test.
1 second for fuel pump prime is about right when you turn the key to On with the stock ECU or PFC.
With the fuel pump resistor relay you should see 9v at idle/low load and around 12-13 at high load. You can tap a multimeter Into the fuel pump wiring and drive around to test.
Dale
Dale, I have around 5.3V at idle. I have not checked it under load, but plan to do that soon. Please let me know of any reason you could see my voltage being that low at idle. Not sure if a failing relay can act as a resistor, so I'd like to know everything you know. Please share!
Dale, I have around 5.3V at idle. I have not checked it under load, but plan to do that soon. Please let me know of any reason you could see my voltage being that low at idle. Not sure if a failing relay can act as a resistor, so I'd like to know everything you know. Please share!
Do you have the FSM schematic for the fuel pump circuit? It'll be on page Z-28 of the '93 FSM/wiring diagram. If you trace the current path for the fuel pump circuit, you'll count a total of 11 series connection points between the output side of the 20A fuel pump fuse in JB-03, and the fuel pump's ground point. That number of connections (11) is the same, whether the fuel pump relay is energized or not - i.e., current flowing to the pump goes thru the fuel pump resistor or bypasses it (flows thru FP relay instead).
At idle, the FP relay is not energized, and pump current would flow thru the FP resistor's path, and any one of those connection points can be corroded, burnt, loose or otherwise adding some resistance. Since it's a series circuit, if just a few of these connections are bad, you could easily be down to the 5.3V you're seeing. And yeah, the FP relay can act as a resistor if it's contacts are burnt or corroded enough, but in this case (idle), current would be flowing thru the resistors instead.
Do you have the FSM schematic for the fuel pump circuit? It'll be on page Z-28 of the '93 FSM/wiring diagram. If you trace the current path for the fuel pump circuit, you'll count a total of 11 series connection points between the output side of the 20A fuel pump fuse in JB-03, and the fuel pump's ground point. That number of connections (11) is the same, whether the fuel pump relay is energized or not - i.e., current flowing to the pump goes thru the fuel pump resistor or bypasses it (flows thru FP relay instead).
At idle, the FP relay is not energized, and pump current would flow thru the FP resistor's path, and any one of those connection points can be corroded, burnt, loose or otherwise adding some resistance. Since it's a series circuit, if just a few of these connections are bad, you could easily be down to the 5.3V you're seeing. And yeah, the FP relay can act as a resistor if it's contacts are burnt or corroded enough, but in this case (idle), current would be flowing thru the resistors instead.
Great advice., thanks!!! I have the FSM (one of the PDF versions), and I will try to trace this down through the connection points. Another thing I am considering (because I do track my car in wet conditions), is relocating the front relay box. I think I will try to do this all together. Trace voltage and also extend the front relay box wiring harness. Since my battery is relocated, I will try to put the box somewhere in that space.
I suspected one of the main relays (circuit relay and /or EGI relay), as they were original to the car. I ordered them new from Ray, and popped them in. No voltage! There had to be another problem, so I started with fuses and wiring. As stated before, I ran the Chuck Westbrook parallel line, from battery positive directly to the circuit relay socket (I de-pinned and capped the thick blue wire), and added an inline fuse. Checking that fuse, I noticed that it was cocked in the holder. I pressed it in firmly, and voltage!
Still not convinced, I called a friend to make sure I could get a tow home and today I set off to make the voltage cut again. After driving around my neighborhood (close by my friend's house), the voltage cut happened again! First thing I checked was that fuse. The fuse holder is very close to the intercooler core, and I figured the fuse holder rubber housing was heating up too much and the connection with the fuse was being lost and/or the fuse was backing-out. I brought a zip tie for this exact scenario. I cinched the fuse into the holder with the zip tie, and checked - I had voltage! I made it home, but I am being told there still may be an underlying problem. I'm working with my local rotary guru, but my plan is to ditch the in-line fuse, use an empty socket set in that box, and make a cleaner connection to battery positive. Maybe not the root cause, but I feel like the cleaner installation may be in order anyway. So far, it's been 2 unnecessary fuel pumps and possibly 2 unnecessary relays. I will update as I figure this out.
Those cheap in-line fuse holders from the parts store can be problematic. I have a feeling that could be the root of the problem.
Factory wiring is typically very reliable, there are some things that could be better (voltage drop) but it's reliable. Typically when there's problems it's due to someone messing with it - aftermarket alarm, big stereo install, relocated battery, etc.
Those cheap in-line fuse holders from the parts store can be problematic. I have a feeling that could be the root of the problem.
Factory wiring is typically very reliable, there are some things that could be better (voltage drop) but it's reliable. Typically when there's problems it's due to someone messing with it - aftermarket alarm, big stereo install, relocated battery, etc.
Dale
From what I've seen so far, I'm the only person that messed with any wiring in the car. I agree that the factory wiring should be pretty sound, but I am getting seemingly low voltage at idle. I get mixed comments on that. Some say the lower voltage is not a big deal, but my local rotary guru is saying I should investigate. As was suggested earlier, I guess I'll bite the bullet and trace the wiring with the FSM wiring diagram. Speaking of which, does anyone have a descent place to download a better version than the old scanned copy that is readily available?
Did some continuity testing today. I only followed the path that the current will take during idle / low-load conditions. I ran a baseline continuity by touching the multimeter leads together as well as touching them to the ends of a very short run of wire (3"). Result for that was 0.3-Ohms.
The test path was as follows:
- Battery positive post to Circuit Opening Relay socket (This is the line I ran per the Westbrook directions, and has the problem fuse holder body in it). Result: 0.3-Ohms
- Other Circuit Opening Relay socket (This is the blue w/ red stripe) to the same color wire pin on the fuel pump resistor connector B1-05. Result: 0.4-Ohms
- Fuel pump resistor connector B1-05 pin white w/ red stripe to fuel pump connector (rear hatch) B1-06 with same wire. Result: 0.4-Ohms
I will try to drive it around tomorrow, and report back. Yesterday, I moved the fuse holder body to the other side of the battery positive fuse block, away from the heat of the intercooler. As of now, I suspect that the issue was just the cheap AutoZone in-line fuse wire, but there still has to be a reason that I see 5.3V at the pumps at idle / low-load instead of the reported 9V. I can only assume that this is a result of the FP resistor, as there is nothing else in that path causing more than 0.1-Ohm of resistance over the baseline.
If anyone has any comments, concerns, suspicions, things I missed, or other suggestions, please let me know!
Since my last update, I did more testing. The in-line fuse wire, after I cinched it down with a zip tie, wound-up popping. Finally thinking that was the problem, I decided to get some ATO terminals and use an empty slot in the relay/fuse box as has been outlined in this forum already.
...Still not convinced, I took the car out for a few test drives around the neighborhood. Surprisingly, no break-downs/fuse pops.
Fast forward to today, I decided to drive to friend's about 25-20mi away, and avoid interstates. Half-way there (I goosed the car a little here and there), power loss again! Prepared with plenty of extra fuses, I popped a fresh one in, and decided to drive very carefully to my friend's place to try a little troubleshooting. My friend didn't have an ammeter, so I was not able to test, but I noticed a few things:
1. When I first popped the hood after it cut, I heard a weird noise that I can only compare to the noise that the wastegate/turbo pre-control solenoids make if you disconnect the MAP sensor from the harness connector. After a short time, it stopped.
2. The fuse was hot, as were the resistor fins.
My current thoughts:
My two Walbro 450LPH pumps (model F90000267) are drawing a lot of current, and I am not sure that running a dedicated relay (using the ECU 1K signal to switch) for the high-load path with be the absolute solution. I suspect that, even if I did that, the low-load path through the resistor would still be overheating. I checked the FP resistor when I did continuity testing, and it appeared to be within spec, so I can only assume that the fuel pump current draw is just too much with both pumps running in parallel.
I know a only work colleague that built a pretty gnarly fuel system for his F-250, using a variable frequency drive for his fuel pumps. Wondering if anyone around here has experience with VFDs.
Finally...
I want to know how anyone else, running multiple fuel pumps in their FD, has set their system up. Any details are appreciated! For now, the testing continues.
Final update (and a word on aftermarket, high-flow fuel pumps):
In speaking with some smart people, I was given the idea to talk directly to Walbro (TI Automotive tech. support) and ask about the low-load path and running the pumps at low voltage. I was told that the 450 pumps should not be run at any lower voltage than 9V. Since I am measuring 5.6-5.75V to my pumps (and the resistor fins measured at 200F within 1.5 minutes of just starting the car!) I have decided to use race car pumps how they were intended to be used. 12V all the time, through a relay. Now, some folks may be asking, "Quichedem, why you running dual Walbro 450s on your rinkey-dink 310RWHP car?!?" Back when I had even more money than sense, I bought one of B2A's surge tanks off the classifieds and it came with those pumps. Since my tuner tuned with that, it's what I'm stuck with (for now).
My plan moving forward:
I'll be having my local shop wire-up a relay to my fuel pumps, using the original FP voltage line (the white / red stripe) as a trigger. Also having them wire-in some warning lights in the event I lose voltage to a pump. I'll run these pumps like that, until they burn-out, then I will replace with appropriately-sized pumps and re-tune (and maybe go back to the stock voltage paths). Until that time, I will consider this case closed.
If you are running, or plan to run big fuel pumps, be sure to NOT use the stock FD wiring to supply power to them!
You've gone too far down the rabbit hole at this point but at that power level a fuel pump swap should NOT require a re-tune.
If you are using the stock FPR, that is what is setting your fuel pressure. A larger pump is needed at higher power levels since the injectors are dumping more fuel into the engine - if the pump can't keep up, pressure drops.
To be on the safe side, watch AFR's when doing a few pulls and make sure they stay where they should be, that's it.
But, if you've got your setup working, just leave it be
in your dual pump setup is one for lift (low pressure) inside the tank and the other for pressure to the engine? You can use the stock wiring for the low pressure lift pump as it will draw low amps at low pressure. But you need dedicated wiring with relay for the pressure pump. I'm using Radium's
Saw a few recent threads on fuel pump issues, so I figured I'd make an update since it's been quite some time since I've sorted this out.
First of all, I have ditched the B2A surge tank kit for now. I'll outline my plans for that in a bit. I installed the well-documented Aeromotive Stealth back into the stock hanger, and have been issue-free since. Got some genuine Walbro 450s taking up space in a box now. May put those up for sale soon.
My future plans:
Eventually, I will install the B2A surge tank, but I will set it up this way:
* Keep the Aeromotive Stealth as the "send" pump. No wiring change, and the voltage path will stay the same as for a completely stock configuration.
* Add another Aeromotive Stealth as a "lift" pump, but this will run on a separate and dedicated circuit sharing nothing with any stock fuel pump wiring.
* For the lift pump circuit, I intend to employ a resistor, similar to the stock resistor or even use a stock resistor. This pump should never need to run full tilt, especially since the return from the engine goes back into the surge tank.
Eventually, I will document this here when I get around to it, which I may try to do this summer. Just wanted to remind everyone about the perils of over-sized fuel pumps.
good plans!
I'm running Radium's surge tank setup, using a Walbro 450 on stock wiring (and stock resistor pack) to feed the tank and a Walbro 525 as pressure pump on a dedicated 10ga circuit directly from battery.
I'm using the stock pump's +12V to trigger the relay so the pump primes and runs as stock.
Curiously, I was running a Walbro 400 on stock hanger and wiring before and it was quiet as stock. Now I can hear the pumps and the whoosh of flow through the fuel lines
01-31-21, 09:26 AM
