I did a carb swap on an 85 302 t-bird with an in-tank pump and a TBI. The in tank pump was rated at 88 LPH and the pressure was about the same as any FI application. Maybe only slightly less. You can get pumps rated up to 250 lph if you modify the engine. Not knowing which engine you have, the regulator is at the fuel rail, which you will be removing.
There have been numerous posts about these swaps. You probably have the fuel return line back to the tank as well. You will need a 3-port pressure regulator (I used a Mallory) to regulate the pressure back down to carb PSI. 1 port will be the feed from the tank, 1 port will go to the carb intake (through the regulated port), and 1 port will send the overflow back to the tank. There is a jumper wire you will have to add (I dont recall from to where) or the fuel pump will not run for more than a second when you turn the key on. For heavens sake, dont go into the harness and do a bunch of "cuttin" and "removing". Later, you or the next poor person will regret it. Fold them back and sleeve them.
The trucks use the low pressure pumps in the tanks to feed the high pressure one on the frame. The cars didn't have this set-up. A return line is a good idea. The gas 85 460 F250 trucks used the low pressure pumps in the tanks to feed the OEM 4bbl. They had a Y block in the metal fuel line to split off to the return.
I think the low pressure in-tank pump should be sufficient for a carb provided it is rated for enough volumn. At 12 psi, it is more than what a carb needs. You will need some sort of in-line regulator with a return to the tank for excess fuel, I guess the Y block had a regulator in line to keep pressure up. If the low pressure in-tank pump is continuous running, then it must be controlled by the PCM (or whatever) and will have the impact shut-off safety feature. You will still need to determine if a jumper is needed to keep the pump running after initial pressure up when the key is turned on.
If you havnt removed the FI setup yet, why not try to measure the fuel pressure at the rail/regulator before removing it. I believe the 89's were all multi-port injection (could be wrong), so I kinda wonder why you want to swap. Its your business to swap if you want, and LOL, but you maybe should consider that this swap is with some headaches and the carb is not as good as the FI setup (.02). LOL anyway
Yep, 89's are all EFI running 32 to 40psi at the rails. The EFI is more efficient than a carb.
I don't remember how the 85 truck with the 460 operated the pumps, ignition wise.
It had no regulator, just whenever the floats closed, the excess pressure bled off through the y-block and back to tank. It may have been internally metered, I never had it off ot look.
Yep, looks like anything with a continuously running pump capable of over 40 psi would certainly need to be regulated down with a 3 port regulator for a carb. It actually worked pretty well on my 85 bird, but it had a full feed/return line all the way to the TB.
That 460 setup sure looks curious----. I'll bet there is a regulator of some sort in that "vapor valve". It wouldnt seem to need to be any larger than a brass "T" ftg unless something else is in that housing. I just dont see how a back pressure of ~5-7 psi for a carb could be maintained if that bypass leg is not regulated to provide the backpressure. Even if the pump was a ~40 psi pump I dont see how a straight "T" would work.
Of course you dont know where where I am getting my information---I didnt say . I have the same problem and for the same reason, 8 PSI ?? Please read my post a little more carefull---"Even if the pump was ~40 psi pump--". I dont know what a 460 pump puts out for pressure, but I must disagree with you until I see what your source is. Lxman1 said ~12 psi for those pumps, which I do not argue with. My point was that even if that pump put out from 8 to 40 psi, I think it would require a regulator of some sort. Otherwise, the system would have no backpressure and would be open and not develop much pressure at all (this is just my .02). It is the regulator that determines what psi is developed, the pump has to be capable of both psi and volume.
Old low pressure in tank pumps OEM ,were rated at 60 LPH and went to 88 and even 95 LPH for HO's and DOHC cobras were even 150 LPH. My source says that the operational pressure on all was ~39 psi but could be adjusted on up (dosnt say the absolute upper limit). There is an internal pressure relief valve in the pump that is 138-123 psi for blockages depending upon low/high pressure pump. So much for the OEM pump being limited to ~40 psi.
I would be willing to bet your next paycheck (not mine ) that in the picture of the "T" ftg there is a spring loaded check ball that regulates the pressure and is not adjustable---apparently.
BTW, my source is "The Official Ford Mustang 5.0 Technical Reference & Performance Handbook", (a Ford SVO publication) in addition, Haynes and every other performance publication backs up the ~40 psi figure. So if you disagree, write to them. Again, I dont know what the 85 460 pump does and "Frankly Scarlet" at this point.
Do you know anything that will help the original poster with his carb conversion?
You do not seem to understand the fuel system on an 89 truck at all.
Sounds like you may work with cars and not trucks.
This pump in the tank pumps to a fuel selector valve and puts pressure directly on the diaphragm that the Ford Shop manuals say never to put more than 5 PSI of air on them while testing the switching or you could bust the diaphragm.
Putting a gauge on the fuel line from the tank into a blocked head will give about 7 PSI.
The hot gas bypass (vapor) valve has no moving parts and does not reduce fuel pressure to the carb. It has three possible orifice sizes to return fuel to the tank to stop vapor locking. If you would check the image I posted above you would see the Ford part number for each size.
This system was used on a lot of the RV's in the 80's and I have worked with few of them.
You obviously have not worked around any of these fuel systems on RV's or the 1986-1989 trucks.
Not sure why you would list "The Official Ford Mustang 5.0 Technical Reference & Performance Handbook" as it has nothing to do with the subject we are talking about or the truck the OP is asking about. There would be no information on this subject in that book.
I only use Ford Shop manuals and as far as the Haynes manuals go I have found them good to start fires with and would not own one. Too many errors.
The bottom line is he does not need a regulator with his 89 F-series truck as long as he bypasses the high pressure pump on the frame.
You are not reading my posts, apparently at all. I never make a claim that I understand all about trucks, except that I have a 93 5.8 bronco, SFI, SD system and understand very well how it functions. While that isnt an 86-89, I have no doubt they are similar and are also similar, not exact, to the cars.
With all your input about working on pumps and air pressures, you still have not told us what the output rating of an intank pump on a truck is. If you know, please post it, that will help the original poster with his conversion. If you dont, then quit trying to pick the FlyS*** out of the pepper by challenging me over what I did not say. My suspicion is that you dont know all you claim and are like so many folks that work on things that we have to take home and fix. I could give a rip less about repair procedures at this point, unless I have one.
As I said, regardless of the output of the truck pump, the system requires some way to create backpressure to feed the carb at even 5-8 psi. I alluded to a pressure regulator that I suspected (never said that it actually existed) in the system. You have just given how that (backpressure) occurs and it functions the same as a "regulator" just as one mounted on the CFI or fuel rail would. It appears to me, without a total study of your diagram, which is a little difficult to see the function of all components, that the orifices function as the regulators. Even if you are regulating "Vapor" you regulate everything in that tube, including fluids (fuel) to the psi figure governed by the size of the orifice. How is it that you, as an expert/professional did not see that?
If you know any facts and specs for the truck the poster was talking about, post them and help him. I did not see that he was talking about an 85 460 truck anyway. Quit trying to pick me for what I did not say and help the man or just get out.
First off an fuel delivery system for a 93 5.8 bronco, SFI, SD system is in no way similar to a fuel delivery system for an 89 F-series with any size engine.
See diagrams below.
As far as the pressure goes from a in tank pump I have never seen it given in any Ford Shop manual so I have to go by what a pressure gauge says when you hook it to it. That seems to be about 7 PSI. The only thing I have seen in the 89 Ford Manual is never to put more than 5 PSI on it while testing it.
The pressure stays the same if the hot gas bypass “T” is there or not. The in-tank boost pump may have a regulator in it, I will go in a little while and saw one apart to see what is inside the pump.
The reason the 460 was talked about is what LxMan1 said in post #4 above and I was giving a little more information on the subject.
I dont think that we are very much in disagreement----. I do think because you misread what I was trying to say, that you assumed that I was implying that I was comparing all to each other. I do not, nor did make any statements of fact about earlier model trucks except to say that I suspected they were similar. I said that I didnt know. It may be good info for someone if you cut into an 85 pump to determine if it has some sort of regulator in it. My suspicion is that somewhere in that system is a provision of pressure regulation------damned if I know what it is, but I said that already. I wonder if the manual says not more than 5 psi, are they talking about to the carb, because of the needle and seat or are they talking about reverse pressure back to the pump. Dont know, just asking. As an example (simple, but the best I can think of right now) take the regulator/pop-off valve off of your air compressor and put in its place a straight piece of 3/8 in copper tube and see how much pressure it builds. Not exact, but in principle, it will behave like a fuel system with a bypass and no regulator. Pressure does not come from the pump, but from the regulator. Obviously the pump is needed too.
That 89 diagram does confirm that the 93 system is very much, almost exactly like the 89. In 93 the "high pressure" pump is in the tank, no low pressure pump, no dual tanks and no switch-over valve. Guess I better qualify that statement, MY bronco does not have dual tanks!! All the rest is darn near exact! The pressure test point is the "Schrader" valve on the fuel rail or at the CFI.
Without a manual, for the earlier ones, I believe (.02) that the operating pressure is ~39 PSI for all of them. If there is an internal pump protection valve, then it is probably like all the rest, it goes up to ~125 lbs. The manual I referred to earlier does make references, frequently, to the trucks. Very interesting that the GT40P heads are worth about 10 HP better than the OEM GT40 heads on the cobras (W's). Those were originally on the 97 1/2 explorers. I didnt say that, they did.
For sure, I dont think we are far enough off to be taking up this much time, sure isnt getting his carb swap done . LOL
i did precisely what you are talking about when i swapped my capri to a v8. it worked, but it couldn't keep up for some reason when i would open up the secondaries, I added a parts store pump and regulator and it does just fine for my little 302.
1973 f250 highboy 4x4 http://thelostdrifter.com/index.php/...ducing-trigger1984 full size bronco, -DIS, wide band megasquirted 300/ 8 speed
1988 f150 extended cab 4x4, mostly stock.
1984 mercury capri, 5.0 conversion, my little monster...
1961 ford falcon, all stock, in family since '68
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company.