Fuel pump troubles

[EagleMark]

Even though your regulator is on return side referring to pressure on return side is after regulator, which should be 0 PSI.

Your correct about pressures and 21.5 is not the issue. Pump is designed to run more, I and many people have run TPI pumps for years without issue. Even ran 3/8ths line from a 5/16th outlet on tank, but never smaller. The issue of not enough fuel will show up at WOT high RPM if it can not deleiver fuel because of hose/outlet size.

The outlet or fuel line will not cause the voltage drop. In an LT1 data log you can see sytem voltage and fuel pump voltage, can you in EBL? If you have 1.5 volts drop at idle it may be worse under load. I'd be chasing the electrical end before the fuel line end at this point...

[pmkls1]

I'll cover all 3 of your areas of concern, but first I will start with what I am sure is the cause of your fuel pump failures. I am certain that without a doubt your fuel pump failures are due to wiring issues. I want to stress to you the significance of the voltage drop you are seeing. Just remember that an electric fuel pump is just an electric motor attached to a small set of gears. Electric fuel pumps are designed to operate at 13-14 volts regularly. They will obviously oerate outside of that spec and regularly do, but not continuously. Bottom line, nothing will burn up an electric motor of any sort at the rate you are experiencing other than improper wiring or an extreme load. The restrictions in your fuel system will make it difficult to supply your engine with enough fuel on the top end, but they will not load up a fuel pump enough to burn it out that fast. You do have a couple of problems to address but I strongly suggest that you completely rewire the entire circuit for the fuel pump with 12ga wire and good terminals. If you need to replace the relay, you can get a good relay and pigtail from autozone or advance perfectly suited for your application for very cheap. All you need is to look up a fuel pump relay and pigtail for an early '90's chevy c/k pickup. Be sure that the ground for the pump is also 12ga and the terminal is beefy and bolted to a spot that has been stripped to bare metal. I'm confident that once you fix the electrical you will stop burning up pumps. You will still need to address the fuel supply issues though.

To answer the fuel pressure question, I need to first ask you a question. You mention your fuel pressure readings on the return side in your posts. Did you install the aeromotive pressure regulator in the return line and are using that to regulate pressure ? If so, that is perfectly fine, but I am just trying to clarify things. A direct answer to your question regarding fuel pressure is no 21.5psi is not going to cause your fuel pump issues. All of the pumps you have used were intended to run far higher pressures than that. Now, 21psi is getting a little high for the injectors as they begin to behave erratic at pressures that high. But, you are ok for now as your problems aren't related. We can save that for nother discussion.

Now, for the fuel line issue. I don't have a simple answer for you regarding how to solve that issue. The feed line needs to be 3/8 from the pump to the TBI unit all the way. The return line is just fine being 5/16 as that is the standard for just about any Chevy V8 application. In order to solve your problem, you need to have a sender that has 3/8 line for the feed side. You could check the fuel injected 6cyl Jeep senders and see what size line they use. There is a decent chance that the 6cyl senders may have a larger feed line as they would have a higher demand for fuel. If you could find a sender with the proper size line that works with your tank that would be the easiest solution. As far as the rest of the vehicle goes, the simplest solution would be to run a new hard line from the tank to the front. I'm not sure what type of fitting/connection you have for the soft line to hard lines, but a barbed end and hose clamps are just fine for the pressures you are running. If you do end up replacing all of the fuel lines on the Jeep I highly recommend you use "fuel injection hose" for the rubber hoses. You can find fuel injection hose anywhere including autozone and advance. Most fuel injection hose appears the same as regular rubber hose but it is not the same at all. Fuel injection hose has a much higher burst strength and is better suited for higher pressures. Even the relatively low 21.5psi you are running is a bit high for standard rubber hose. Fuel injection hose is also engineered to withstand exposure to higher alcohol content and other chemicals as is normally encountered with modern gasoline. HTH,

Phil

[mike327]

Ordered some seal tite connectors and a few other parts from Dell City. It will be about a week before I can get back on this...work calls.

[mike327]

Ok time for update. I ran 12 gage wire for power,changed the relay to 12 gage also and ground, no voltage loss like I had before. I did not run new fuel line yet but plan to plumb with 3/8's hard line and hose. The Jeep does have a stumble when I "floor it". I see no pressure drop @ this time. I will start running some data logs and VE learns to see if I can tell whats going on. Thanks for the help guys.....more questions to follow.

[pmkls1]

I saw your last post several days ago, but my schedule hasn't afforded me the time to reply until now. Glad to see that the wiring change resolved the voltage drop issues. That should eliminate the issue with it eating fuel pumps. Because the line is small, you won't see a pressure drop, just a lean condition under high loads. That is because the smaller line will cause a volume issue. If you had a restriction like a kink or something to that effect you would be able to see a pressure drop on the other side of the kink when the fuel demand rises. In this case the entire line would be the "kink" so the pressure drop would be at the injector theoretically. Anyway, what you are describing sounds like it may be able to be resolved with some tuning of the AE tables. If you are experiencing a stumble only when you "floor it" that is similar to a carburetor with a bad accelerator pump then that is most likely an AE issue that you should be able to resolve. Even though the fuel demand is going to spike when you stab the throttle, the type of issue that having too small of a fuel line will cause would be more of a lean miss type issue at WOT and higher RPM's. Say you're running it up to 6000 RPM's and it starts to lean out, that's the kind of issue that the inadequate sized fuel line would cause. I expect that you probably won't have issues that could be attributed to the existing fuel lines unless you are running it hard like I just described. Other than that, as long as your fuel pump continues to operate properly and your fuel pressure stays good, any other fueling issues should be able to be resolved with tuning. When running a "wet" manifold setup like carbureted or TBI, you gotta add a lot of fuel when opening the throttle quickly or a lot or both because the pressure in the manifold rises causing the atomized fuel to puddle. The larger the plenum volume, the longer the runners, and/or the more aggressive the engine, will result in a larger shot of extra fuel when stabbing the throttle. The LT1 carb intake like what you have has a pretty decent plenum size since it's meant to go on top of an engine that can produce nearly 300hp with a good induction and exhaust setup. That is going to equate into you having to get pretty aggressive with the AE settings to feed that beast you've got under your hood. I hope I haven't rambled on too long and look forward to seeing an update on how things are going.

Phil

[mike327]

Just a quick update. Jeep has been running fairly well this past week. I've had it on the gulf coast @ cruisn' the coast, riding up and down the beach looking at all the cars in town. A ton of cars from TN. I was having trouble keeping it running in all the stop and go traffic so i reset fuel psi back to 13 psi and flash a bin that came with EBl. Then I done a few learns and it smoothed out real well all things considering. I just drove it the week cruising around, no burnouts or racing. DC% stayed well below 50% and BLM stayed between 126 and 130. When I get it back home I plan to get down and dirty with this tuning because I have got to be able to do a little racing with other Jeeps and a few unsuspecting cars.

Nobody ever post a pic of what they are working on so here it is, nothing special just something to play around with.

[mike327]

Update! The Jeep has been running great as for as daily driving goes. It still needs a little work as for as performance goes. It just does not have the acceleration that the carb had. Why does my timing retard when I accelerate? I thought it was suppose to advance.

[phonedawgz]

The ECM retards the timing when the engine is under a higher load - ie at a wider open throttle. It advances it when the load is lighter (higher vacuum aka lower MAP sensor readings)