GSRICK

New owner here with a '77 and my first posts outside my intro thread. The previous owner built the engine up and decided to try out FI Techs 400hp kit with the Command Center. The Command Center is basically a canister that the stock mechanical fuel pump sends the fuel to and then an internal electric pump sends the pressurized fuel to the throttle body. The engine starts with just a push of the button(like a race carl) and idles great. Starting out it runs strong, but I'm still taking it easy as the engine really has only 50 miles on it and hasn't really been broken in yet. It is the original 350 small block built to 355 and about 310 hp.

I've take it on a couple of short test rides and have had it stumble and shut down after just a couple of miles. This last trip I had my son manning the hand held controller to collect data, so we could see what was happening. Sadly I found out at the same time, as it was getting dark, that my battery wasn't all that good and when it shut down the voltage was too weak to restart it this time and I guess we didn't wait long enough for the data to be saved. After getting a new battery from the closest source Wallyworld, I tried to drive it home only to have it barely make it, having to stop two times, because it was struggling to keep up any power. When finally I limped it into the driveway, I popped the hood to look at the pressure gauges on the Command Center. Both the low pressure gauge and high pressure gauge were reading near zero. I've read about Command Centers vapor locking, but it doen't seem to be running long enough to get that hot and the fuel line from the mechanical pump runs between the header and oil pan, but I don't think it close enough to get very hot, especially side these are side pipe headers and aren't anywhere hear the oil pan.

I've read that the mechanical pumps, put out somewhere around 3-7 psi and the electric pump should be in the 55-60 psi range. Has anyone else used this FI system and had this trouble? The owner mentioned that this had happened to him, but said he read about a fix and supposedly did the mod to fix it. Apparently it didn't do the trick. He purchased the alternative in-line electric fuel pump for it and gave it to me with the car. If I use this it may solve my problem, but I may have to modify the fuel tank outlet pipes if they are not 3/8" tubing.

With that said, I thought about maybe getting an in-tank electric fuel pump like you would find on a newer car, but I haven't found any listed for the C3 fuel tanks. Did any of the later C3 cars have EFI and maybe a pump in the tank? Would a C4 pump work in a C3 tank? To me this would be the best route since it is quieter than an in-line pump and would last longer being since it is cooled by being submerged in the fuel. Any tips or links to an in-tank pump will be greatly appreciated.

Haggisbash

I have been considering the FiTech system and I believe there is an in tank pump available as an option if you don't want to use the Command Centre or inline pump. There is also a fuel tank with pump available from tanksinc. I have read about the vapour locking issue, how hot is too hot? Before I gave up on what you have installed I would be trying to determine the exact cause.
I found this on the web -Gas doesn't typically "boil", but it does vaporize (evaporate) at anything over 93 degrees F or so. As I understand it, the "boiling point" of regular 87 unleaded is about 181 degrees...but this will differ depending on pressure and what additives are in the gas.
What was the "fix" that the PO employed?

talentscout

My friend has had several fi-tech fuel injection set ups and I don't believe it works with a mechanical fuel pump, You need an electric fuel pump and it can be in or outside the tank. Call the manufacturer and ask them about the requirements for your system. We made several calls and they were very helpful. You
can buy a new gas tank direct bolt in with electric fuel pump I believe they are around $500-600. Try Holley they build one.

RBrid

Sorry about your troubles GSRICK. As far as I know there is no catalog out there that offers an in-tank electric pump solution for a 1977 vette like yours. I believe any such approach would have to be custom-built.

talentscout, the FiTech system does work with the mechanical fuel pump as long as you add their Command Center system with its high pressure electric pump or some alternative system like http://www.robbmcperformance.com/products/powersurge.html.

worship79

" The Command Center is basically a canister that the stock mechanical fuel pump sends the fuel to and then an internal electric pump sends the pressurized fuel to the throttle body "

Metalhead140

Ok, well I use the Fitech, with the FCC. If both your gauges are showing low, then you're not getting fuel to the fcc, you have an issue on the low pressure side. Could be vapour lock before or after the mechanical pump, could be the mechanical pump is bad, could be a fuel filter blocked, or an issue with one of the fuel lines. But the problem is definitely before the fcc. How did he setup the fuel lines, and what did he use for the vent line back to the tank? I am using a high output mechanical pump without the bypass/return fitting, then I'm using the original return line from the mechanical pump as my fcc vent. I guess it might be possible that you have an issue with the vent from the fcc, causing pressurisation of the fcc and not allowing fuel in, but the gauge readings imply to me that the low pressure side is more likely to be the problem.

I don't believe it's related to your problem, but note that Fitech recommends lower than default pulse width settings for the fuel pump control when using the fcc - that will help to avoid the fuel pump heating and boiling the fuel in the fcc, but if he has truly done the 'fcc mod' then you should be ok anyway - the mod is to remove the float inside so that the fuel is constantly circulated from the fcc back to the fuel tank, keeping it cooler. I have done this, but only because I was replacing the pump, my fcc worked fine as shipped for 20,000+ miles.

GSRICK

Metalhead, I'm guessing he did the FCC mod you mention, but I'm not 100% on that. The mechanical pump looks to be a stock small block Chevy type of pump and from the outside appearance it looks new. I plan on trying to work on it this Sunday when I'm off work again. I want to disconnect the power to the FCC to prime it up with the mechanical pump like what would be done at the initial install and see what the low gauge pressure reads. I don't know if my son was reading the hand held right when I was driving the car, but he said that when it started loosing power that it looked like the system was dumping fuel in it. I hadn't thought about that until just now, so I'll to see what he was referring to.

The car still has the stock metal fuel lines from the tank to the mechanical pump and the supplied fuel line from there to the FCC low pressure in. Then fuel line to the TB from the high out line. The vent line runs over across the firewall and down towards the bottom of the car. My son looked under there before we went on the test ride, but couldn't tell where the line went for sure, but says it went to a steel line that ran to the back of the car then up behind the seat. The mechanical pump return line is still hooked up to the steel return line at the pump on the passenger side, but I don't know how it's routed under the car. We were running out of daylight and I wanted to hurry up and get some data to send to the FITech tech, but that didn't go as planned.

Metalhead140

When the system is starving for fuel it will try to dump more fuel in, because it will be running lean. So the trims will be high positive numbers, but the afr measurements should show it running lean (unless it gets to the point that it's so lean that it doesn't fire a cylinder at all, and dumps unburnt fuel in the exhaust).
​​​​​​
When running, the FCC gauges should show ~60psi on the high pressure and 3-7psi on the low. Having said that, the low pressure will read lower if the modification has been done to the fcc, but mine still reads around 3-5psi.

Metalhead140

You can check if the mod is done to the fcc by taking off the vent hose and feeding it into a container. If the fcc has been modded, there will be a constant flow of fuel into the container with the engine running. If the fcc has not been modded then little to no fuel will flow into the container.

Metalhead140

There is another line from the charcoal canister back to the tank that maybe the one that was used for your vent line?

GSRICK

Thanks for the info on the pressures. It gives me something to go by.

By what I described, does the the fcc vent line sound like it is hooked up right? I'm not sure why there would be a steel line running on the opposite side from the mechanical fuel lines. Sorry I can't give a better description. I'll jack up the car and take a look myself Sunday and see whats going on.

GSRICK

Ok, if it is, is the charcoal canister line able to be used for that? How did you run your vent line?

Metalhead140

I'll bet it's the charcoal canister line then. I imagine it should be ok, but I don't know if there might be a restriction or valve in that line. I actually teed my vent to connect both to that line and the factory return line from the mechanical pump, but using the factory return line from the pump requires changing to a pump that doesn't need the return line. The reason I teed into both lines for my vent is that a lot of the issues people have had with the fcc have been to do with the vent lines, and I wanted to ensure that I wouldn't have problems.

This was the pump I used: https://www.summitracing.com/int/par...6900/overview/

Instructions for setting the pwm of the fuel pump to suit the fcc: https://fitechefi.com/wp-content/upl...thpictures.pdf

GSRICK

Thanks MH, I found something similar checking out tanksinc website looking for a FI tank. http://www.tanksinc.com/pdf/SettingF...Tech_-_Web.pdf
They listed a tank for the '68-74, but not the later gen 3. Do you know if there is a differance in the tanks after '74?
http://www.tanksinc.com/index.cfm/pa...rod/prd443.htm
I'm hoping I can solve the problem without spending more money, but it's an interesting alternative to think about. Being that I live in FL, I'd like to put AC back in the car. The fcc is currently occupying that area.

Metalhead140

There is a difference in the tanks, but I'm not sure what the differences are or how difficult it is to change between them. I believe the earlier cars have smaller fuel tanks than the later ones. A few people have put modern efi pumps in 1982 hangers inside stock later tanks, but this means you can't run the tank low as there's no baffles and the fuel will slosh away from the pump pick up. Depending on how you use your car, this may or may not be an issue for you. My fcc is down low in the driver's fender, under the brake master/booster, where the charcoal canister originally was mounted.

Gordonm

GSRICK

Looks like you already have a buyer, Gordonm. If it doesn't work out let me know, I may be able to swing it. Still would like to get this system working as the majority seems to see this is a good system. It may just be a simple problem I have to locate and cure.

Gordonm

Gordonm

RBrid

You must be talking about https://www.zip-corvette.com/70-74-g...separator.html. GSRICK's '77 does not have one. I think there would be a free flow into his tank.