walton99 Posted October 28, 2015 Share Posted October 28, 2015 Howdy yall. I've been having some odd under-fueling issues and I think I've come up with a way to ensure that it's not the pump. I've got '80 NA body with a swapped in '82 L28ET. The motor has been pulling strong and rich since the swap approx 15k miles ago. Recently she's been running really lean, especially at WOT. I'm also getting a distinct pulsing in the fuel lines, especially noticeable at idle and an erratic idle that surges from 250rpm to 800rpm. This also is leading to the engine dying on me whenever I try to come to a stop, such as at a stop light or downshifting for a slow corner. I'm running a Pallnet fuel rail with stock turbo injectors, an aftermarket FPR (Tomei Type-L) and a Walbro 255 pump. I picked up a painless fuel pump relay kit and plan on installing it this weekend. My question is if I will run into any problems tapping into a ignition 12v source as opposed to the signal wire that is currently going to the pump. My thought is that way I will have a cleaner signal and possibly be able to bypass whatever issues are causing the pump to surge. What do you guys think? Quote Link to comment Share on other sites More sharing options...
FricFrac Posted October 28, 2015 Share Posted October 28, 2015 A relay is an on/off switch. If you give it a signal to turn on its on (unless of course you can supply enough current to turn on a relay which is less than 100mA). Check and verify what you think the problem might be. If you suspect power to the pump then check the voltage at the pump. We do a lot of custom relay and fuse block assembly that plug into the stock body harness for MegaSquirt and other stand alone EFI systems. For the 81-83 we reverse the control logic and run the stock relay. On the 79-80 with the larger relay we make an adapter harness and drive the fuel pump directly through the large fuel pump relay near the headlight sensor in front of the passenger Strut tower. Quote Link to comment Share on other sites More sharing options...
FricFrac Posted October 28, 2015 Share Posted October 28, 2015 Adapter cable plugs into the stock body harness to connect to the 81-83 style relay kit. Quote Link to comment Share on other sites More sharing options...
walton99 Posted October 28, 2015 Author Share Posted October 28, 2015 A relay is an on/off switch. If you give it a signal to turn on its on (unless of course you can supply enough current to turn on a relay which is less than 100mA). Check and verify what you think the problem might be. If you suspect power to the pump then check the voltage at the pump. We do a lot of custom relay and fuse block assembly that plug into the stock body harness for MegaSquirt and other stand alone EFI systems. For the 81-83 we reverse the control logic and run the stock relay. On the 79-80 with the larger relay we make an adapter harness and drive the fuel pump directly through the large fuel pump relay near the headlight sensor in front of the passenger Strut tower. Thank you Sir, I appreciate it. I'll check the voltage at the pump. The only problem is that she is running just a bit rich (10.5-11 on wide band at idle) and the issue only manifests at higher rpm under load so i wasn't sure how to go about checking voltage at the pump as the rpm increases. I'm pretty familiar with relays but not nearly as familiar with the ECU, so I wasn't sure if bypassing that fuel pump output would send a bad feedback loop to the ECU and cause something funky to occur, hence my hesitation. That’s a beautiful harness, if I ever go to a megasquirt I’ll definitely look you up and order some of your products. Thank you again. Quote Link to comment Share on other sites More sharing options...
FricFrac Posted October 29, 2015 Share Posted October 29, 2015 Just run some extra wires from the fuel pump to the meter and put it on the dash, etc and you can monitor the voltage as you drive. You can use a small gauge wire as you are drawing a very small amount of current in the meter. You can check out some of our projects at www.mackaypowerproducts.com Running a stand alone EFI system is the ground work for optimizing the performance and fuel economy of your engine. You also have the added benefit of being able to monitor what is happening as well as data logging and analyzing after your run. You could also for example add a fuel pressure sensor to the rail and monitor your fuel pressure which would make resolving your current problem a lot easier. Quote Link to comment Share on other sites More sharing options...
walton99 Posted October 29, 2015 Author Share Posted October 29, 2015 I appreciate it sir, much obliged Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 30, 2015 Share Posted October 30, 2015 So you want to forego the stock Fuel Pump wiring as the signal (I assume you have not used the fuel pump modulator and this pump is either on or off, full speed)... You want to substitute straight Ign 12V for the relay signal. What if you run headlong into a tree, are knocked unconcious and a fuel line breaks? How does the pump shut off? The stock pump will. Using the stock wiring to trigger the relay retains the accident shutoff function for the fuel pump. If you wire it straight, use a Ford Inertia Switch to kill the pump should you get hit, hit something, or roll over. Quote Link to comment Share on other sites More sharing options...
walton99 Posted October 30, 2015 Author Share Posted October 30, 2015 So you want to forego the stock Fuel Pump wiring as the signal (I assume you have not used the fuel pump modulator and this pump is either on or off, full speed)... You want to substitute straight Ign 12V for the relay signal. What if you run headlong into a tree, are knocked unconcious and a fuel line breaks? How does the pump shut off? The stock pump will. Using the stock wiring to trigger the relay retains the accident shutoff function for the fuel pump. If you wire it straight, use a Ford Inertia Switch to kill the pump should you get hit, hit something, or roll over. That's a good idea, thank you Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 31, 2015 Share Posted October 31, 2015 You can do that conversion using the Ford switch. If you can find one from a Tempo-Topaz, they literally have close to 3' of heavy gauge wiring to salvage out of the harness. It's a direct disconnect inline to the power to the pump--it's that heavy a contact set. But it would work famously in the control circuit of the relay as well. They are also found in the passenger footwell of Ford Rangers near the trans tunnel under the floor mat. These are the same switches sold by Pegasus Racing. I have run my 240 with the salvaged wires out of a trunk-mounted Topaz from fuse box to fuel pump using the salvaged Ford Wiring, and mounting the switch on the vertical surface parcel shelf near the trans tunnel, with the wiring using the 280Z Grommet exiting almost exactly where the stock 280Z Fuel Pump Wiring exits. I can jusssst reset it from the drivers seat while harnessed, if necessary. With the standard 3-Point belts it's easily reset. We would play 'bumper cars' with rental Topaz's and Escorts...a good bump from the back end on those trunk mounted switches and the switch will trip and require resetting. Great way to freak out the new service guy with the company making him immobile and driving off from some distant airport and no clue how to get to the job site other than "follow us!" BUMP hehehehehehe.... Quote Link to comment Share on other sites More sharing options...
walton99 Posted October 31, 2015 Author Share Posted October 31, 2015 Thanks Tony D, I appreciate it. I'll head the the local bone yard monday and see if I can't find one and wire it in. Quote Link to comment Share on other sites More sharing options...
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