I've upgraded my carb'd vehicle to TBI and am trying to go with an inline pump on the frame rail. I'm starting to think I have a fuel delivery problem. I'm reading 10 psi at the throttle body, which I think is on the low side. The main thing that's bugging me though is that I have a lot of air circulating around in my fuel filter, which I have before the pump. Is it not right to have the filter before the pump like this? On one hand I don't want to make the pump suck through the filter or suck air, but on the other I've seen the garbage the filter has caught and I don't think I want that going through the pump. What's the right way? This is a nice self priming Carter pump by the way.

This is an action shot with it circulating a bunch of air around in the filter.

 

I've run that pump with a filter before it at least 30 times in person and know of 100's of others with no issues. 10 PSI is not enough on an accurate gauge!

If when it's running you see air bubbles circulating, not just a bubble on top, then you have a loose connection somewhere from the filter to the tank and it is sucking air!

Since everyone is told to run 3/8th line from tank to TBI unit and the stock fuel tank on a carb truck is 5/16ths this is probably where your issue is.

If you have not taken out the tank and cleaned the sock on bottom of pickup tube, or replaced, I remove them because I run the filter before pump. It will cause a severe suction and can collapse hose!

Rule for pump is below bottom of tank. That is false. If you read the instructions on that TBI in line fuel pump it can be mounted 2 feet above tank. Lower is better. Their is also an identical looking pump for TPI. One id PN5000 one PN5001

EDIT: If that is your ground wire to fuel pump I see it also needs to be put at least to good clean conection on frame and frame needs to be grounded to engine and engine needs to be grounded to body. These are always EFI conversion issues. I run a ground wire from pump to block.

 

Get rid of the carb-type fuel filter and use an EFI filter (10 micron). Place it after the fuel pump.

If the pump inlet doesn't have a mesh screen/filter then place one prior to the pump. A 100 micron filter is enough. I use a stainless steel mesh filter that I put together.

10 psi is within the service range of a TBI set up, which is 9 to 13 psi.

An inline pump should always be as low as the bottom of the fuel tank. Although I have gotten away with doing worse then that. But it was stock engine, would never have done what I did for a performance engine.

RBob.

 

Thanks. I'm sure I have the sock thing on the pickup in the tank, do you think that's sufficient prior to the pump? Regarding and EFI style filter for after the pump, do you happen to have a part number you can throw out? I'm not sure what to ask for. I assume most EFI setups would have steel line after the pump, but I'm running rubber.

 

Your supposed to have a steel EFI filter after the pump as well...

But even with the sock on pickup in tank you will notice the before pump filter still gets dirty. For warrenty to be valid you need to put filter before pump, it's in the instructions as well. I always buy a pump and filter on same receipt.

GM says a lot of things. One is 9 to 13 PSI for a TBI engine. That is also wrong. If it ain't 13 it ain't never gonna run right. Yeah it'll run. But your trying to tune it right and that will never happen until you get 13 PSI.

 

So what kind of filter do you run before? Do you put one after? I've never replaced a submersible pump in a tank, but I expect they have no filter before them, just the sock. Otherwise you'd have to pull the tank to replace the fuel filter at some regular interval.

Not sure what to do here. I've had nothing but grief from this system from day 1, and I've always had a filter like this before it. I'm really inclined to see what happens with it out and a factory TBI filter after.

Oh, and you seriously bend custom steel all the way to and from the throttle body on TBI conversions? I don't have it in me to even think about that. I have major league high pressure flex line on my setup.

 

You can run steel line all the way but need fittings at each end, fuel filter goes in the middle. Go to junk yard and both feed and return off 1987 to 1991 Blazer. Grab the tank too and you'll have your in-tank pump!

In tank pump has a sock on bottom but it is way better then the screen in a carb type tank.

The way yours is done is correct except you need a EFI type metal inline filter after pump to further clean gas and not clog injectors. EFI filters as RBob mentioned above are much finer.

But if you are circulating bubbles in that pre filter you are sucking air. Pull the tank, flush it, loose the sock. Run 5/16th line from tank to 5/16th filter and get a 5/16th fitting for back of pump or do your conversion to 3/8 there with double claps. Regular fuel line is fine to pump. Must have EFI rated line after.

 

I'm in the process of putting an EFI filter after the pump now. It's one of the canisters with female threads on both ends. I can't figure out how to make it seal. I have these nice push-lok fittings I'm trying to plug in but I can't make it tight enough not to leak. Crappy design if it relies on the threads to seal. Push-lok doesn't work that way.

I ran it for a minute even though it was dripping and the fuel pressure was wandering around 11-13 or so. Maybe it was trying to work the air out. I haven't dropped the tank yet; it could be sucking air at the sender.

 

I'm pretty sure I can hear air hissing through the fuel line prior to the pump. At this point I need to drop the tank and find out what's going on in there. I think I'm going to just suck it up and buy a TBI tank, sender, and pump.

Question: what's the rationale for needing EFI fuel line with only 15 PSI? That stuff is out of this world expensive. O'Reilly is asking about $7.50 per foot. It's about $3 from Rock Auto but the shipping is ridiculous. The EFI fuel line is rated for multiport systems (hose is good for 180 PSI).

 

If the regulator fails or return line is blocked the pressure will exceed regular carburetor fuel line...

Looking at some older conversions I've done or worked on regular carb fuel line works but has visible cracks after a year or so. EFI fuel line looks new after several years. So I think there's a big difference in quality as well.

 

They do seem higher quality, but it may just be cosmetic. The non-EFI stuff is rated for 50 PSI, do you think a TBI pump really puts out more than that?

Do you have a good source for the EFI hose?

 

I've used stuff from NAPA that was rated 45 psi and burst at 90 PSI and it was cracked, rotten and looked like **** at a year. Hard as a rock.

When I do a conversion on a customer car I bend lines entire distence and have a company crimp/silversolder ends on end which are usually GM. $250 is nothing compared to the $40k car I am working on...

 

$250 is a lot to me. My Blazer is in great shape, but still I'd be lucky to get more than $6k for it.

I'm starting to warm to the idea of running more hard line. I should be able to easily run it from the tank to the filter and then some length after that. It would start to get hairy going up into the engine compartment, so I could stop along the way someplace and change to EFI line. Do you put any sections of rubber in for isolation between the tank and frame, or can you go with hard line all the way?

 

If money is the issue just fix what you got! It'll work without a leak sucking air.

Or if you get a newer blazer EFI tank from Junk Yard get all the hoses and hard lines. There will be a flexable line off tank to frame, hard lines up to top of transmission and stailess braided lines to TBI. Fuel filter is in middle of truck.

 

If this is the filter I think it is, they are Saginaw fittings and use an o-ring to seal. Uses a metric thread too. The filter I am thinking of is GF481.

RBob.

 

Yeah, I got Wix 33481 which must be the same. It didn't come with o-rings. Is it the thing where the o-rings are captive on the end of the male fitting?

3/8" went right in, so I'm surprised it's metric, but maybe it was close and the tolerances were loose.

Just looking at the picture of the sending unit I ordered, it looks like it has a male fitting with captive o-ring on the output. Will I be able to find steel line with the needed fittings at a regular parts store?

Thanks for the help guys.

 

You can buy short lengths of line with the fitting on it as repair pieces. Can also grab from a JY. Be sure to put a bead on the end so that the hose doesn't push off. I do it by melting solder onto the end of the line.

Fitting looks like this and is 16mm x 1.5mm. Can see the o-ring on the short narrow end piece.

RBob.

 

Thanks for the help. I saw that Dorman has various repair sections, but everything I've found is male end like your picture. Looking at the sender I ordered:



it looks like there's a male end on there too. Any thoughts on how to get from that to steel line? Does the factory use steel line with a female end, or something else?

 

Factory truck uses braded line from there to hard line it is crimped on.

 

So what have you been doing on retrofits? Or have you not done many in-tank pumps?

 

I've done them all? I even ran a mechanical pump into a quart size fuel filter under hood then inline pump to TBI on a low HP engine and never had an issue.

Problem with an in tank pump in a regular gas tank is no reservoir or plastic bucket in bottom to hold fuel and when you hit 1/4 tank and go around corners fuel will slosh and you stall... same with a regular carb type pickup and inline pump like you have but it seems worse because usually you do not get the sock on bottom of tank. I've seen some mounted couple inches from bottom and they get the slosh issue at half tank...

Newer pumps are spring loaded in plastic tanks and press down to bottom of tank when full or empty and flex up and down an inch or so. There are also some that have a bucket on bottom that stays full till the last drop because of return line keeping it full.

I don't know and doubt the sender you pictured is going to fit the hole in your tank?

What I am doing right now on my son's IH truck is cutting a hole around the existing fuel sender hole and I have a few GM TBI sending unit/fuel pumps I cut out of EFI tanks with a big square so I have the sender unit mounting hole and about four inches of metal around it, plenty of room to trim to hole we make in his IH tank. Then weld it in. Yes this can be done safely if you know how to prepare and weld fuel tanks. We are doing his this way because the GM fuel pump sending unit is an inch to long, so we will shorten it to rest on bottom of tank. Also going to use GM truck fuel lines from TBI back to tank. They are to long so we will probably shorten them at the fuel filter and re-flare. Got all these parts off a 1990 one ton four door dually with dual tanks, dam tank almost fit without the work.

For yours... I would fix what you got! Has worked fine many times before.

If I had to do it from scratch I would find a 1987 to 1991 Full size blazer and grab the tank, feed and return lines to TBI.

 

I'm buying a new tank too. I need one anyway, so I'm getting an EFI one with baffles or whatever it's supposed to have. I'm copying 1991 basically. I'm just stuck on how to get the connectors I need to connect to the sender and fuel filter. I'm not really keen on driving an hour across town to scrounge 15 year old used parts if I can avoid it.

I found an Earl's fitting that will at least connect to the male saginaw fitting. It's AN on the other side, so I can probably do something with that. Maybe just go to rubber line if I can't figure out anything better.

http://www.summitracing.com/parts/EAR-9894DBJERL/

 

You thought $7.50 a foot for EFI hose was expensive? Wait till you get done with all the AN fittings and braided line... you only got one so far at $10.99 an inch...

You can buy all the metal fuel line and fittings needed from parts store. I get metal fuel line in 50 foot rolls but i have a fuel line bender and flare tool. You can also buy straight lengths of fuel line already flared with fittings, then would need the coupler between each piece, I found a metal EFI filter once that went in between these lines.

It's a days work to make feed and return lines. Then I'm lucky enough to have a guy in town who does hydraulic hose fittings and repairs so I add them to each end to connect to TBI and fuel tank. So there's flexible braided line at each end.

Or you could fix what you have?

 

The ship has sailed man. I need to replace the tank anyway. This is the time to go with a proper in-tank pump. The tank, sender and pump are in the mail. I just need to deal with the fuel routing.

Do you really mean to say I can get pre-made lengths of fuel line with the saginaw style ends (rubber o-rings)? If so, that's absolutely how I'll go. I can't find any reference to anything like that searching on-line. I still need some sort of adapter to attach flex line between steel sections (and sender), that's why I got to looking at that fancy AN fitting.

 

What? Like this?
http://www.rockauto.com/catalog/moreinfo.php?pk=622474

 

Or like this?

Here is a list of fuel line fittings, adapters, and some
other handy parts for GM EFI conversions. This list is
primarily for Saginaw (metric O ring type) fittings. This is
updated to add part no's for Earl's fittings and Weatherhead
fittings.


fuel injection feed and return nut kit GM 1711798
thread sizes are 14mm X 1.5 and 16mm X 1.5

Connector, fuel feed, double female lines GM 15544805
connects two male 3/8" Saginaw ends
Connector, fuel return, double female lines GM 15550219
connects two male 5/16" Saginaw ends
Short sections of line, approx2", with metric/quick connect
ends
Pressure: GM#15694407 $10.55 list
15609225 short, straight $2.55
15609224 short, u shaped $3.25
15694408 $10.55

These fittings can easily be used with rubber line by using
the quick connect side as a barb. Be sure to use quality
clamps and hose rated for appropriate pressures.

Stainless steel braided hose, feed and return
15567762 approx. 30"long $72 list
This line is used on '88 and '89 pickups. Looks nice and
it's flexible, but spendy.

rubber hoses
22527471 fuel feed, 1 male X 1 female 3/8" ID
22528623 fuel return 1male X 1 male 5/16" ID
10114736 return hose female X female 5/16" ID
10114709 feed hose female X female 3/8" ID
These are hoses which connect between the tank and the
lines. There are many different versions available, and
they are all model specific.

O rings
22514722 fuel feed
22516256 fuel ret.

Fuel Filters
25055052 or GF 481 (AC) standard efi filter
25055003 or GF 478 (AC) 1983 Camaro with Crossfire (5.0 "S"
engine) barbed hose end on inlet and 3/8 inv. flare on
outlet
GF626 has same fittings as GF481, is stainless steel (not
polished), and costs less! Fits 1995 Chevy pickup.
______________________________________________________________________

Motorvac Fittings
MV0603400: fuel feed m16X1.5 to 3/8" inv. flare $16.50
MV0603304: fuel ret. metric14X1.5 to 5/16" inv. flare $15.04

Available through Snap On Dealer
Motorvac Tech Support (800) 841-8810
(I will use these, and have ordered one of each)
_________________________________________________
Accel Saginaw parts:

JUMPER LINES:
"The kit consists of three 12" long, 3/8" diameter steel
tubes and one 12"
long, 5/16" diameter steel tube with the Saginaw flare used
in stock GM fuel
injection systems. It allows direct connection to TPI fuel
rails and a high
pressure fuel filter." (one end has Saginaw fitting, other
end is unfinished)

Jumper Line Kit:74731
3/8" Jumper Line Only:74731-A
5/16" Jumper Line Only:74731-B


HOSE BARB FITTING:
3/8 Saginaw/Hose Barb Fitting (2 ea):74720-A
(for both sides of a high pressure fuel filter, e.g. AC
GF481)


FUEL LINE FITTINGS:
"High quality aluminum fittings provide perfect fit to adapt
GM fuel rails
(Saginaw) or high pressure fuel filters with Saginaw flares
to AN-type
fittings."

Fuel Filter Fitting Kit: 3/8 Saginaw to 6AN (2 ea):74721
TPI Fuel Rail Fitting Kit: 3/8 Saginaw to 6AN (1 ea), 5/16
Saginaw to AN (1
ea): 74730


HIGH FLOW FUEL FILTER & PUMP FITTINGS:
"Anodized in a rich gold, these fittings allow the highest
flowrate of any
Saginaw fitting available. Complete with O-rings, these
fittings now accept
#8AN fuel line."

High Flow Fuel Filter Fitting: 74743-H
High Flow Fuel Pump Fitting: 74711-H
Fuel Filter with 3/8 Saginaw provisions: 74720 (like GF481)
_______________________________________________________________

Weatherhead Fittings

3/8" inverted flare to 14 X 1.5mm 1445
3/8" inverted flare to 16 X 1.5mm 1446
3/8" inverted flare to 18 X 1.5mm 1447

_______________________________________________________________
Earls (1-800-421-2712)

part no.
991954 14mm X 1.5 (return line)
991955 16mm X 1.5 (pressure line)
991956 18mm X 1.5 (power steering line)


These fittings adapt to a -6 AN line.
_________________________________________________________________

Remember that part numbers and prices often change, that
parts are sometimes discontinued or replaced by "similar"
parts, and that any EFI conversion requires a certain amount
of ingenuity and flexibility.

Fuel feed lines in stock applications are typically 3/8"dia.
and return lines are typically 5/16" dia.
Some EFI conversions use Saginaw type line ends cut from
stock lines and attached to standard steel line with
*quality* compression fittings

These fittings have their roots in hydraulic applications,
and shops which make hydraulic hoses may be able to find
Saginaw ends to make custom lines.

 

Thanks, I'll have to take some time to look that over tonight. I saw the Dorman part on Rock Auto, but I couldn't tell what was on the other end. Another fitting, or bare steel? If it has fittings on both ends, then all I really need is fitting to get from male saginaw into rubber hose. Maybe something like that is on your list.