NEED HELP with Fast efi set up

[*71SWB*]

I've posted many times before I am a NON-MECHANIC and hope that I can explain my need correctly.

I have a 71 SWB C10 and purchased the Fast EFI master kit. Once the shop did the install the truck would run great for a short time and then lose preasure which caused the truck to cut off or bog down then cut off. They called FAST and were told the fuel pump was bad. I purchased a new one from them and plan on returning the defective one.

They then installed the new fuel pump and the truck did the same thing again. They again called fast and during conversation the mechanic was told the tank needed to be pulled and to have an in line placed on the top and an exit line on the bottom of the tank directly under the in line so the were in line with each other. The man from fast explained the pump does not suck the gas. I paid to have the tank removed and these lines placed in.

The truck was placed back to gether and ran great for about 50 miles. Then when I picked it up and had gone about 10 miles it did the same thing again. The mechanic checked all the readings and they are indicating as they should. With the engine running the preasure is at 43 and when you tap the gas pedal the preasure drops to below 20. My mechanic is telling me the fuel pump is bad again that the preasure should not change with pressing the gas pedal.

My mechanic will be calling fast today again. I'm hoping someone can shed some light for me. Is the pump bad or what else should we look for. I can't keep spending money. This system and install has cost me a ton....

Thank you for any help and I hope I've been able to explain this well enough for a mechanic to understand.

[truckdude239]

Try a different brand of pump also check for rubber fuel lines colapsing

[71tahoe]

Originally Posted by truckdude239

Try a different brand of pump also check for rubber fuel lines colapsing

And that the tank is properly vented. If it can't get air in it will pull a vacuum in the tank which will counter the pressure the pump produces.

[jrdv]

I hate to hear your having trouble. I love my Fast EFI.

I put mine on myself and it has had zero problems so far. I agree with truckdude239 on the possibility of the hose collapsing.

Did the shop use the hose that came with the kit? Did they just tie into the hard fuel lines or is it all hose? Is the pump within 18 inches of the tank? Is your gas cap vented?

I used all rubber EFI hose for both fuel lines. Mine is tied into a toolbox/gas tank combo ( It is a 4x4 ).

I really don't think it is your pump.....what are the odds of getting 2 bad pumps? It just sounds like a fuel starvation issue to me.

John

[88Ironduke]

Everyone here is giving good advice. Have you actually verified fuel pressure at the fuel rail? Adapters are available thru Jegs or Summit racing to have a gauge that stays in place. Also have a look at the power supply for improper wire sizing and ensure that the ground source for the fuel pump is clean and in good condition.

88Ironduke

['68 Newtricks]

All good advice, but you really need to read the FAST directions yourself and look over the shop's work. You never know what could be going wrong.

I ditched the FAST hoses. Too hard to work with and had a couple leaks. I have a hose manufacturer close by. I had them crimp and make all the lines I wanted, rated up to 200 or 300 psi, can't remember. I put this on my 85 blazer, using a 91 tank and sending unit (91 has fuel injection) The stock TBI sending unit will hold a stock Delco pump from a TPI camaro. (50-60psi) TBI pumps are only like 20 psi, something low like that.

The first pump I used was a Walbro. Terrible pump, really loud, and kinda ended up doing what you are describing. It would run fine first half of a drive, sometimes stumble and want to die. Other times it would stumble right away. Most of the time I could drive it a solid 2 hours before it acted up again. Good first 100 miles, terrible next 2 hundred, and in the trash after 350 miles. Replaced with an AC Delco, factory Camaro TPI unit. Quiet and trouble free for the last 2000 miles. When the old pump acted up, the computer would sometimes throw an ERROR code. O2 Sensor. After much frustration trying to hunt down a problem where there wasn't one, I finally figured out it was the pump.

Where is your pump (now two pumps, which isn't necessary) located? If you are running an inline pump (external) it HAS TO be mounted below the gas tank and as close to it as possible. The problem with the cab mounted tanks is the supply line is really high. This could cause problems like FAST mentioned. If you can do an in-tank pump, that would be best. What did you do about the return from the regulator?

Also, make sure the vacuum hose going to the regulator is coming from the correct port on the throttle body. (read instructions) I set my pressure to 45, with the motor running, but not connected to vacuum. (instructions say this) Once the vacuum line is put on, the pressure drops a couple psi. So your 43 to 20 sounds really weird. Probably a supply problem (aka pump, obstruction, collapse hose, voltage drop, bad ground)

*deep breath*

ok, who knows if any of this helps. Keep us updated. The FAST guys are helpful but only as good as blind help can be. You really should read over the directions and call FAST yourself with the problem. Even if you can't work on it yourself, you can write down what they say and be more knowledgeable when dealing with the installer.

[jaros44sr]

Did you try to post up the problem on the fast forum, alot smart guys on there. May be able to diagnose the problem for you

[tranz am]

I would suspect an electrical connection is at fault for this. make sure all the connections are solid throughout the entire system. Not just in the fuel system also check the truck wiring specifically at the fuse box connections and ignition switch. I had a phantom problem like this before and after months of frustrating stumbling issues hunting my truck and pissing me off, I finally figured out it was the damn ignition switch with the loose connection causing me all the grief! Who would have thought right? Sometimes its the smallest of things you don't think about. Check the ignition switch , It might just be the culprit.
also don't forget to check your ground straps from the frame and body. Make sure the shop soldered all your wire connections too.

[*71SWB*]

Sorry for the delay in responding. We (mechanic did) contact FAST and after reviewing how everything is hooked up, the hoses used, and many other checks and balances they requested, they have determined it is the pump again. This time they are replacing with an upgraded pump. Not sure why as they current should handle it. I guess we will see when it arrives and is installed. I sure hope this works. The truck ran so good beofer it didn't. lol Thanks everyone and i'll keep you posted.

[tranz am]

I kinda doubt its the pump but i guess its possible. If it still does this after the new pump I would still check what I mentioned.

[67 chevelle]

check and recheck you vent , a faulty vent would do exactly what you are describing

[RManson]

Proper tank venting and wiring are the most obvious things to check.

Where is the regulator mounted? Is it mounted after the injectors? If not, the system won't see proper pressure.

Are you using the stock in-cab tank? The pickup is at the top of the tank and perhaps a frame-mounted pump wouldn't like this setup (especially without proper venting). I modified my stock cab tank to EFI and it worked flawlessly so it's possible.

['68 Newtricks]

update?

[*71SWB*]

Sorry for the delay in updating everyone. The issue seems to have been the tank itself. The truck sitting for 7 years produced a lot of rust. New tank installed and system working great. Still a little nervous but so far it is all good.

['68 Newtricks]

Yeah, that will do it. But really, the rust should have shown up the first time, in the pre-filter. Here's hoping the injector or post filter are clean.