What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

FI Upgrade questions and concerns

TommyD11730

TommyD11730

1/2 ton status
 Premium
Joined
Oct 3, 2014
Posts
454
Reaction score
51
Location
NY
Hey Guys

I never thought I would say it, but it's time. Having driven my TBI equipped 91 K5 for a couple of years now the 4V on my 84 K2500 has to go. Don't get me wrong, the 84 runs decent enough, it's just the 91 TBI runs that much better.

Some info on the 84 I want to convert. 1984 K2500 350 4V 700R4 no AC, pretty much bare bones stock. I recently removed the pass side tank (leaking) however the selector system was working up till the time I pulled it.

I'm leaning towards the FITech system vs a stock system from Howell or the likes. Though I do have some concerns like....

My 700R4, will I have problems connecting it to the FITech system? I believe I also have a vacuum/electrical switch (load?) that assists on the trans. Hopefully the FITech throttle body will accommodate it.

Fuel deliverly is another concern. I'm guessing it would be "easy enough" to install a baffled 87 tank and upgrade the pump to a high pressure in tank. However where do I go from there? I can't possibly retain the stock transfer valve. Just wondering what other guys have done.

If I'm "stuck" running just 1 tank what will I need to use for fuel lines? Not crazy about the modern plastic type. Steel feed/return lines seem more my speed however how do you attach them to the sender or TBI for that matter?

Thanks for all your help!
 
TBI has dual tanks with selector valves also, it's only 13psi of fuel pressure not exactly a modern high pressure system. I'm running the stock carb valve in my TBI swap. You can run external pumps or in tank stock style TBI pumps, honestly the TBI pumps are cheaper and easier to work with plus you get new sending units out of the deal
 
I would think even 12psi would blow a rubber hose off with a worm gear clamp.
Guessing if I ran the FITech TBI unit I could connect their external pump after the valve. Use their supplied AN8 line from the pump to the TBI. Then I could plumb the return back via the factory steel vent line??

Honestly im not crazy about external pumps... but its better then their awful fuel sump system. Well I saw awful as I had something similar on a Mercury outboard.
 
high pressure efi pump and external pumps draw fuel best as close to tank as possible. putting them to far away = not good.

why not 1 efi tank/efi sender/96 c3500 vortec 350 pump direct fit to our senders and then use 2nd tank as transfer tank for long trips. this is what I will be doing .

fitech is 58psi spec. the vortec pump is about 65-66 all out. and a few fitech units have built in regulator so much faster to plumb it in with less fittings and external regulator in the mix . since its a built in regulator .
 
My experience to transfer tanks is limited. I helped maintain a fleet of 1995 HD3500 back in the day. To say the least the GM system was troublesome.
I dont think thats a route I want to go but thanks for the idea.
 
12 psi is fine with rubber line and worm clamps, I ran my lines that way for a while before I got around to improving the situation. Never had an issue, just did it till I finalized the way I wanted to run my dual tank setup. I'll change it again when I swap to a Blazer tank in the near future.
 
Just wondering... how did the factory plumb the tanks to the selector valve on the 87up TBI trucks? Did they use plain old rubber lines? Or???
 
Most of it is hard lines, the connections were short lengths of rubber hose with clamps. Same at the tank pressure and return connections. They really were (almost) the same as the carbed trucks from the cab back. The lines route to different areas once they reach the engine bay.
 
TommyD11730 said:
I would think even 12psi would blow a rubber hose off with a worm gear clamp.
Click to expand...

As mentioned, that's how GM did it, except I believe all those were the spring clamps, not worm gear.

Dunno if it was/is some DOT reg, or just GM being safe, but it appears anything with a passenger area over the fuel system (K5 and Suburban) used fittings instead of hose clamps, even though the fuel system was the same otherwise.
 
So I could run 2 in tank pumps... use rubber FI lines from tanks to switching valve... then come up with some sort of a hard line, using rubber fuel line to connect to the TBI unit?
 
TommyD11730 said:
So I could run 2 in tank pumps... use rubber FI lines from tanks to switching valve... then come up with some sort of a hard line, using rubber fuel line to connect to the TBI unit?
Click to expand...

That is what GM did for the pumps.

I'm not partial to rubber fuel lines, especially under pressure, personal thing.

I hate those switching valves, I'd rather setup the two tanks along the lines of what SweetK30 said and get rid of the valve.
 
My other fear is now sending 15 or so PSI into a valve from 1984!
Your going to laugh but as I have the passenger side tank out if I go GM style TBI I'll just put an 87 tank pump in, and run on 1 tank alone.
Like I mentioned, never liked the fuel transfer systen GM used (that I worked on) so I think that's out.
 
I would like to know how a vacuum/siphon system would work in practice.

I worked it out in my head and somewhat on paper, and I tested it, but the variable I couldn't test was fuel return. With a "passive" system like I was thinking of (use passenger tank as primary, fuel is taken from the secondary/drivers tank via siphon as the primary draws down), if not plumbed right, the returned fuel might be able to overfill the tanks. I think a simple tee in the return line would solve that, but I don't have the need nor truck to test it out on.
 
So I have given this a decent bit of thought. If I go the aftermarket route it's a easy 1600$ or so from the likes of Howell or what not. My reservations of going aftermarket is 5 years down the like the "module" craps the bed and its no longer available. So at that point I'm SOL.

I'm leaning towards buying a 89-91 Burb as a donor. Does anything prevent me from just swinging the motor complete with FI into my 84 (has 700R4 but I believe it's vacuum vs electric)? Any surprises like balance issues? I don't need the AC from the burb so hopefully someone makes an idler setup to of in place of the compressor.
Might as well steal the rad support, grille and buckets too....
Come to think of it, if I steal the harness (fuse block and all) steering column, cluster and any under dash boxes/modules) I would have cruise control as an upgrade 2... yes???

How about front doors... are they the same as far as door panels and the likes go?

My truck currently has intermittent wipers however I believe the module from the late models are different. At least the plugs look different.
 
Most of the TBI system in my 85 came from an 89 burb.

Yes, you can use everything from the burb that's how I did it. It's actually easier than trying to piece it together. You can use the cruise, wipers, everything you want. If you don't want AC and it's the hybrid v-belt system just don't install the compressor or belt. If you have a serpentine setup there is a factory idler bracket that replaces the compressor, we use them for field repairs on HMMWVs and M1008s that are still in service. It was also factory installed on non-ac serpentine belt trucks and van throughout the GMT-400 series as well as s-10s and astros.

Not a hard swap, but a lot easier with a complete donor.
 
So use the flywheel from the donor TBI motor.. yes??

Can I.. should I also "upgrade" my 700R4 to work with the electronic speed sensor? No idea what that even involves and as so much as my trans shifts up and down just fine.... not sure I want to mess with it.
 
CK10 also what did you do about your tank (s). I gather the burb will not have a dash mounted rocker switch for the fuel tanks. Anyone know if that part of the dash harness is stand alone (like say how the dash clock harness is) or is it integral on my 84.
 
TommyD11730 said:
So use the flywheel from the donor TBI motor.. yes??

Can I.. should I also "upgrade" my 700R4 to work with the electronic speed sensor? No idea what that even involves and as so much as my trans shifts up and down just fine.... not sure I want to mess with it.
Click to expand...

Use the flywheel from the engine that you use, easiest way to guarantee it's the right one.

If you get an 89 burb donor it's a mechanical speedo, otherwise it's your call on electrical or mechanical setup. If I had the electrical setup that would be the one I would choose, mine is mechanical because it's what I had and it works.

Fuel tanks you will have a few options:

1) install the burb tank behind your rear axle as is with all its plumbing and connections (if your truck is a shortbed the 40 gal tank won't fit, but a 31 gallon will. burbs come with both)

2) run one saddle tank with the pump/sender from the burb adapted to it and bypass the selector valve.

3) run the dual tanks you have with 1987 v10 pump/sender units in them through your stock selector valve, this is what I did. Works great, but I would rather have a big single tank in the rear if I had one available to me.
 
You must log in or register to reply here.

Latest Posts

Top Bottom