The stock pump is 255lph ish at 60psi.
CK5
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'86 Jimmy 4in Lift, 40’s, tons, 8.1 Swap- 700r4 said PNNNNN
- Thread starter GWeakland620
- Start date
This is not a dedicated trail rig, but does trailer to the destination usually. I am currently in the planning phase of doing a 52/56" spring swap, and getting back to being more road worthy.
Can you share where that spec comes from? At 67 gph, that's clearly more than the 48gph frame-mounted one, but like air compressors, it's good to know what pressure the flow is at and vise versa, since they're not always the same operating point.
Lower pressure = higher flow right? Over simplifying a pump curve. My information is based on the Walbro 255 which is interchangeable with the stock LS pump.
I didn't make any claims about the pump curve, just questioning the numbers since there was no source. Many of us are using the EP381, which is rated at 155lph and is good for >400HP. Just because you can use the Walboro pump doesn't mean all LS pumps have to do 255lph.
I didn't realize the EP381 was 155lph. I thought it was the same.
Isn't the EP381 for originally Vortec trucks or TPI Camaros?
Yes TPI
And those didn't need more than 155lph
Yes, that's about what the early 2000's LS-based Vortec truck pumps were rated at (hence people say they're good up to 400 or even 450HP). I can't find a rating for the flex fuel pumps, but it is a different part number, suggesting the flow is higher (nobody lists the pump PNs anymore, just the modules). Taking "400HP" with 30% more fuel required for E85 would be less than the ratings of the 5.3/6.0 engines.
I'm using a stock 6.0L pump with my 8.1L, because they are the same part number. I just see in the 8.1L swap resource thread that many swapping 8.1 for SBC use EP381, because it fits in a sender for the square body tank. https://ck5.com/forums/threads/l18-8-1l-swap-resource-thread.308019/page-2#post-3297380
https://help.summitracing.com/app/answers/detail/a_id/5245/~/what-size-fuel-pump-do-i-need?
I'm using a stock 6.0L pump with my 8.1L, because they are the same part number. I just see in the 8.1L swap resource thread that many swapping 8.1 for SBC use EP381, because it fits in a sender for the square body tank. https://ck5.com/forums/threads/l18-8-1l-swap-resource-thread.308019/page-2#post-3297380
https://help.summitracing.com/app/answers/detail/a_id/5245/~/what-size-fuel-pump-do-i-need?
I plan on using the ep381 when I put the 8.1 in my 89 suburban but I am not modifying the engine for high horsepower.
I just want the most torque I can get with a cam and a tune so I am hoping it will keep up
Inching closer to firing this up. Currently fighting an issue with the coil/injector fuse blowing after a few seconds of the keys on.
Tried a larger fuse, and it’s holding now, but I’m still not getting any spark. I checked to makes sure I had my 12 volt cranking hooked to a good source that stays hot durning cranking. Everything else seems right. Going to check for a bad coil or injector tonight to make sure there isn’t one grounding out.
View attachment IMG_4250.mov
Tried a larger fuse, and it’s holding now, but I’m still not getting any spark. I checked to makes sure I had my 12 volt cranking hooked to a good source that stays hot durning cranking. Everything else seems right. Going to check for a bad coil or injector tonight to make sure there isn’t one grounding out.
View attachment IMG_4250.mov
Ok new development. With injector harness completely unplugged, my new 30a circuit breaker still tripped. So I started messing with the coils to narrow them down, and my coil packs are pretty warm without any cranking. Any ideas as to why that is?
Sorry, I forget the history and this thread is long, but I'm pretty sure you're doing an 8.1, which is almost mostly the same as an LS, wiring wise. The coils are fed +12V from the fuse. The ECM provides the ground path. If they are heating, that means there is a constant path to ground in the ECM or somewhere else. But if the harness is not connected, that can't happen, so it must only be disconnected from the ECM side? Do you have a current clamp?
Yes this is an 8.1 with a Howell harness.
Are all the coil packs warm or just 1 or 2 or 1 bank?
You could unplug the ECM and turn the key on to see if they still heat up. If they do it's a wiring issue, if not then it's an ECM issue.
You could unplug the ECM and turn the key on to see if they still heat up. If they do it's a wiring issue, if not then it's an ECM issue.
They all felt about the same.
So a buddy of mine just jogged my memory a bit, and I’m not super positive that I have a good ground from the battery to the block. I know I have a good one from block to firewall, but I’m guessing that’s my issue. I’m off early today so I’ll be looking into that when I get home.
Lol yeah that would make sense if things are trying to ground through the coils and other stuff.
Grounds are important for sure but you aren’t going to pop a fuse if you don’t have the block to battery ground set. The fuse is popping because there is a short to ground.
Like Heath said, the pcm is the ground for the injectors and coils. The block to battery ground isn’t part of that circuit. It goes fuse-coil-pcm-ground. If the circuit is getting ground through another source before the pcm then it’s going to pop the circuit protection. There should be no other source for ground unless a circuit is pinched and grounding out through it.
I’d be looking for continuity to ground on that circuit with the pcm disconnected. There shouldn’t be any, but since the fuse is popping you should find that there is. My bet is a wire is pinched somewhere.
If you want a quick way to isolate it, unplug the coil harnesses at the valve covers. Do one side at a time. If the fuse stops popping with one side unplugged you need to start looking there. If it continues to pop with both sides unplugged it’s in the engine harness. Knowing how many Howell harnesses Larry has used along with my own, I doubt it’s just how the harness was put together but more like something got grounded out by punching together during the assembly process on the engine.
Like Heath said, the pcm is the ground for the injectors and coils. The block to battery ground isn’t part of that circuit. It goes fuse-coil-pcm-ground. If the circuit is getting ground through another source before the pcm then it’s going to pop the circuit protection. There should be no other source for ground unless a circuit is pinched and grounding out through it.
I’d be looking for continuity to ground on that circuit with the pcm disconnected. There shouldn’t be any, but since the fuse is popping you should find that there is. My bet is a wire is pinched somewhere.
If you want a quick way to isolate it, unplug the coil harnesses at the valve covers. Do one side at a time. If the fuse stops popping with one side unplugged you need to start looking there. If it continues to pop with both sides unplugged it’s in the engine harness. Knowing how many Howell harnesses Larry has used along with my own, I doubt it’s just how the harness was put together but more like something got grounded out by punching together during the assembly process on the engine.
I honestly forgot there was a coil harness. I was thinking they were wired straight into engine harness. That’s definitely the route I’ll go.
So I checked my battery grounds, and I must have gotten confused as I had 2 grounds from the battery negative to the frame. I removed the larger gauge cable and attached it to the passenger head. That did lessen my overheating the fuse issue, but it’s still present. I then disconnected the passenger coil harness, and didn’t notice much of a change. I reconnected the passenger side and then disconnected the driver’s side, and the issue seemed to be 90% gone. I checked that harness and nothing is pinched, cut, or has a bad connection. Can a bad coil cause these same issues?
