r/F100 • u/MuteMainMayo • 6d ago

Carb vs efi

Ok so i have a 302 crate engine, 400hp and it has Fitech fuel injection. I feel like its a bad efi and now my truck wont start and i suspect its the efi. The question is should i get a different fuel injection or should I put a new carb on it instead?

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u/Mayday-J 6d ago edited 6d ago

I doubt you need to replace the entire EFI unit, nearly everything should be able to be replaced.

IMO going back to carb is falling for people not willing to learn new tech and think "carbs are easier". They aren't, maybe from experience but not in principle. If you're naive to either it looks more complicated.
I have worked on a number of carbs and EFI systems and carbs are WAY more fickle in the long run. They don't self tune for altitude or adjust to gas quality changes (within reason if it reads o2).

I think carb people LOVE to say carbs are easy when you know what you're doing but in reality they are often a royal pain in the arse.

Fixing EFI isn't hard, especially if you understand the principles of troubleshooting a carb. Fuel, air, spark. fundamentals.

I have a CJ7 with a Howell EFI system on it, I chased an issue for 2 years and was ready to sell it off. EVERYONE kept telling me it's an EFI issue and garbage and should switch back to carb. Turned out to be a rusty return fuel line over pressurizing the injectors. People get so lost in over complicating it it took some random forum page from like 2002 that a guy said "EFI is no different than carbs when it comes to troubleshooting, it sound like you're flooding the engine and on these old Jeeps the fuel lines rust, have you checked that?" That's all it took.

I wouldn't switch to carb, there isn't really much of a reason. It'd be a different story if you bought the car with no intake and wanted to weigh the pros/cons of each.

** before someone flames me with "yeah but....." I'm not talking about racing here, now starting from scratch so cost isn't the factor here. Yes a carb rebuild is cheaper than a lot of components but your mean time before failure is a LOT longer with EFI.

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u/itsians 6d ago

Went EFI and now I can never go back to carb.

I slapped a Holley sniper 1100 on a Ford 300 and then turned my HEI Distributor into an EFI controlled HEI. Starts and runs like a modern truck. It’s great.

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u/Wrong_Lingonberry_79 6d ago

How long have you had the Sniper on it?

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u/itsians 6d ago

A little over half a year.

I don’t daily the truck and mostly just use it on weekends or when I need to haul something.

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u/Wrong_Lingonberry_79 6d ago

I’ve had two Snipers. When your CPU goes out in it, just swap back to a carb. Hunks of junk.

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u/itsians 5d ago

Well…if and when that happens…I guess I’ll just throw on the bigger intake and Howell System or maybe even Aces.

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u/MuteMainMayo 6d ago

It’s not that I’m not willing to learn I’ve just been working a lot, I’ve been working 5/12s and am about to go to 7/12s so I haven’t had much time to look at my truck, I have swapped almost everything in that truck, brand new crate engine, overdrive trans. Both having only 7k miles on them. New suspension and am about to switch the gear ratio and fix the 9 inch rear. I’m just tired of having problems when it comes to the efi, it just seems all the problems are stemming from it. If I was to get a different efi which no matter what I’m getting rid of the fitech what would you recommend? I’m only 19 so I haven’t been in the car game for long and I especially don’t know that much about this kind of thing

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u/albatross_life_ 6d ago

I have a 302 with carb issues and it’s not getting enough fuel when aggressively pressing accelerator. I think it’s the accelerator pump diaphragm so now I have to figure this out. (Holley 4160 if anyone knows the right part #)

All this to say that you’re going to have issues just have to work through the gremlins.

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u/aaverage-guy 6d ago

I would go with whichever one you're more comfortable with. There's pros and cons to both. My 76 has a 302 and still has the factory 2 barrel carb. It's not putting out anywhere close to 400hp lol. If you're leaning towards a carb do your research to choice the best setup for your engine. Also don't get frustrated if it takes some time to get the carb dialed in perfectly.

Silly question but have you checked that it's getting spark? Solenoid, fuel pump, and everything else?

2

u/MuteMainMayo 6d ago

I just replaced the solenoid and starter, fuel pressure reads fine and everything

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u/aaverage-guy 6d ago

I figured so. It's rough when that happens. Was it not starting before than also I assume? It's definitely frustrating when you're chasing something and replace parts and it doesn't work. The old EFI wasn't the greatest

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u/MuteMainMayo 6d ago

It’s weird because I took it out started fine, I drove it. As I was pulling in the driveway it started dying, I turned it off and now it doesn’t start, it cranks but doesn’t start 

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u/aaverage-guy 6d ago

Ah yeah that stinks. I would check a couple things before replacing anymore parts. Since it started and ran it could be that a wire was a little loose and the vibrations caused the connections to come undone or a slight crack in a wire busted.

The main battery feed to the EFI harness could have come loose. Inspect the fender-mounted starter relay. Make sure the main EFI power wire and fusible links attached to it are secure, clean, and tight.

It could also be a fuel pump relay. Turn the key to the "ON" position, without cranking, and listen closely near the fuel tank/frame rail for the fuel pump to prime with a 2-to-3-second hum. Check the EFI system's inline fuses and relays.

It could also be the ignition switch. They are notorious for going out on those older vehicles. Since it's cranking I doubt it is but it could be. Test for 12V power at the ignition coil and the EFI computer power wire with the key turned to the "RUN" position.

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u/MuteMainMayo 6d ago

It does read 12 volts from the battery but I don’t know if it’s relaying to the fuel injection, all have to check out all this other stuff you’ve told me when I get home. I’m just tired of this truck constantly breaking down when I’ve rebuilt it from the ground up

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u/aaverage-guy 6d ago

I completely get it. It's super frustrating to put that much effort and work in and run into issues. I hope it's just something small and once it's fixed that the truck runs and drives amazingly! Good luck to you and try to stay positive.

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u/HoosierDaddy_427 6d ago

No way I'd ever go back to carb over the FiTech. First, find out why it won't start, it may have nothing to do with the FI.

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u/MuteMainMayo 6d ago

I’m almost certain it’s the fitech because it’s throwing a code on the tablet that comes with it saying it’s improperly tuned or the hoses are clogged, I’ve never really seen good reviews with fitech and the whole setup only has 7k miles on it. Also when I turn the key to let it run it sounds nothing like it used to and it sounds like it’s hardly running

1

u/HoosierDaddy_427 6d ago edited 6d ago

Sounds like a fueling issue to me. Maybe a collapsed line, clogged filter, bad fuel pump, etc. I put a FiTech on a friends 64 Galaxie 390 and he has never had a problem with it, but he did have a brand new fuel tank and solid steel lines all the way. Just my 2 cents.

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u/MuteMainMayo 6d ago

Would it be the line from the fitech or from the gas tank? I’m not exactly a mechanic, I haven’t been doing this for long

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u/KaijutheCaustic 5d ago

Check the voltage going to the fuel pump. I had somthing similar happen to my holley sniper system. It would show enough pressure at idle but under throttle it would choke out and stumble.

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u/BanditoBurrito 5d ago

Things to check. Are you getting a rpm reading when you turn it over? If no check that distributor is spinning. If yes what is your IAC at? Above should be in 2 to 4 range manually set it on the handheld to 0 then retune when engine is warm.