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Fuel Delivery Advice

noahrob

noahrob

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So, I converted to my carbed engine to TPI and all was well for a while, but then, wham...started sucking crap into the fule filter. Changed the filter, and the engine was better , but still not getting enough fuel. I have the tank off and will replace it wiht a fuel injection one with internal baffles (and not 30 years of dirt in the bottom), but here is my question. Is there any reason to replace the sending unit? I am still using the stock one and running an external fuel pump.
 
If it's cheep enough would you want to drop the tank again for the price?
 
When i did a TPI swap years ago on a 76 blazer i installed a fuel return tube that went all the way to the bottom of the tank and aimed directly at the fuel pump pick up sock. There was no need for any baffling and it never gave me any troubles.

Having an internal pump is the best thing to do as the fuel helps to keep the pump cool and also makes it alot quieter. If you do keep the external pump it needs to be as close to the tank as possible because electric pumps are made to push fuel not suck fuel.

As for a new sending unit, no reason to replace it unless it doesn't read correctly.
 
I got the new tank and an external pump right up against the tank. I'll stick with the old sending unit and hope for the best...thanks for the feedback.
 
I would highly suggest having a return line welded into the sender and have it go all the way to the bottom and drop right onto the pick-up sock. This will help to avoid any hesitation when you're low on fuel and make a quick turn.
 
Did you just use a little hole saw or whatever and 3/8 inch piece of steel tube? Right now my return line goes into the filler neck.
 
I drilled a small hole in the sender at the appropiate location then used the proper size fuel line and ran it through the hole and then had my local radiator shop silver solder the piece of tube onto the sender.
 
I use a TBI tank and sending unit with a TPI pump in it. Everything goes together fine - no fabrication needed. Fuel gauge also works correctly.
 
Hey Guys,

Here is my thinking...Can I run an intank low pressure pump to feed the high pressure inline fuel pump? Or can I run a full on intake pump throuh the inline pump but keep the inline as a pass through only and a backup? Basically I had no fuel delivery issues for about 75% of th efirst trip out and now I have fuel delivery issues...I dropped the tank and found that the sock on the sending unit had all but disintegrated so need to replace that (Where can I get a new sock for the sending unit?) but now I am on the fence with getting a little feeder pump...which means a new sending until too...dooh!
 
I highly discourage the use of a "Feeder" pump. I tried that with my TPI set-up and kept burning up pumps. Just a high pressure pump is all that's needed. If you must have it on the frame rail then make it as close to the tank as possible. If you buy a new sending unit then get one for a TBI truck and install the high pressure intank pump instead.
 
I have seen 'feeder' pump systems that work though they're usually on multi-tanked vehicles. EB's with 5.0 SEFI engines sometimes do this with a fuel accumulator. The primary reason for doing this in the past has been the lack of availability of fuel tanks that have appropriate EFI baffling. The 'feeder' pump(s) fill the accumulator, and then the high pressure pump draws from that. The key is that the return from the fuel rail be "T'ed" into the accumulator and that there be a slight restriction somewhere so that the feeder pump(s) aren't always running wide open & have something to pump against. Running wide O has been proven in a couple cases to be the reason that the pumps failed.

With that being said, why go to the complexity if you don't need to?

I'm not particularly fond of in-tank pumps from a field repair point of view, but you have to admit that the factory has a simple and effective solution. Granted, the OE pumps have an exceptional MTBF (has to live beyond the warrenty period) so I would highly encourage the purchase of an OE quality in-tank pump (even if that means buying it from the dealership) if that is the direction taken. How much is it worth to you to not have to drop the tank in the field to R&R a pump?
 
The TBI senders seem to have really come down in price (below $100 now, new I think, and used are probably easy to come by as well) so I think that, coupled with a new Delco high pressure pump, are the way to go. Any Delco pump (the same style/shape) that is the same or higher in pressure requirements will work, I believe mine is from a Cadillac. Might be easier to find a decent price on ebay that way.

The Delco Fuel pump should come with everything to change it...sock filter, even the fuel tank sender o-ring.
 
Cool, well I think you pretty much convinced me to get the new sending unit and intank pump...bummer as I have a high pressure inline pump in hand, but I will just keeep that and some rubber line (High pressure) as emergency in field repair parts... I will start looking around for 87 or newer TBI sending units and a 100+psi fuel pump. Thanks for the help.

Noah
 
I've not heard bad things about Walbro, but I see GM pumps on ebay all the time for $75, and I think that's a ripoff lol. :) I don't know what the GM pumps are rated for, 190 might be more than enough for all I know. I'd probably research GM specs a bit more to make sure you aren't paying for something you don't need. It would likely be louder, and more prone to failure (if higher than GM specs) because they are forcing more work out of the same size package.

The sending unit I'd be leery of, unless you can get some confirmation. First off, it's a 25 gallon tank sender (fine if you don't have a 31 gallon tank) and second, they say it fits only '87-88. Maybe there was some change I'm unaware of for '89, but it *should* be '87-91 from what I know.
 
Hey,

Yeha, you are probably right. I have a 25 gallon tank and am just trying to decide the balance between least expensive and most reliable. In other words, I already have a sending unit (just need to get a new strainer/sock/filter thing for the end) and an external pump. I should probably just put it back together and go. My fear is that I will have to do this again in a week or that I am going to continue to have fuel delivery issues....on the other hand, another $100 -$200 for a new sending unit nad pump is not my dream situation.

I'll probably just put it all back together, clean the filter, and hope it works...
 
If that stuff was working before, sure, run it.

It's not an ideal setup, you know that, but since it works (after replacing the sock filter, right?) just keep your eyes peeled for the cheap components to better your setup, and replace yours when/if they fail, or when you get everything you need.

Used 25 gallon TBI senders are probably (should be lol) pretty cheap. I have no qualms about used senders, especially if I can pull it out of the tank and make sure it wasn't potentially damaged. At worst your fuel gauge won't work right, but that won't leave you stranded like a bad pump.

I bet the two year sender deal on Dormans site has to do with the 25 gallon tank. GM probably stopped using 25 gallon tanks in '89, that's why the two year span for the sender linkyou posted.
 
If anybody reads this...thank you! I replaced the tank for one that had internal baffles and ran 10 gauge wire to the fuel pump to make sure it had enough power...this setup worked fine on our way to the Miller trail, in fact, I fell in love with my TPI setup...but then one the way home, same issues, can't rev over 2500rpm without the engine surging 2600, 2500, 2600, 2400, 2500...etc...Any suggestions on what to look at first or how to go about it?
 
I didn't read the whole post but do you have 2 fuel filters or just one? I used 2 filters on my TPI with external pump. I used one low pressure filter before the pump and a high pressure filter after the pump. This way it keeps the trash from the tank out of the fuel pump and is also the cheap filter to replace at about $5 at any parts store.

What kind of pump are you using?

I run a Walbro external pump on my truck with a stock carb fuel tank and a return line plumbed into the filler neck. This setup has worked great for me sofar. The only time I have had a problem is when I was low on fuel at 1/8 tank or less. I would get stumbles under quick turns.

Harley
 
I have the exact same setup except for the pre-pump filter. External Walbro with a carb sending unit, but a brand new baffled tank.
 
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