As the title says, the engine will not rev up and has very poor throttle response.

Here is a list of what I have replaced under the hood:

.40 over
9:1 compression pistions
Hastings rings
Clevite rods and main bearings
Melling high volume oil pump, pick up tube and shaft
Melling timing set
Melling OEM spec camshaft and lifters
Melling pushrods
ARP rod bolts
New 89TM casting heads with new valvetrain and new rocker arms.
Fel-Pro Printo Seal headgaskets
Fel-Pro head bolts
Entire fuel system is new from the tank to the injectors, this includes the tank, low pressure pump(Delphi), high pressure pump(Delphi), new fuel filters both frame rail canister and filter frame mounted on the driver side frame rail, new OEM FPR, OEM injectors were disassembled, sonic cleaned, rebuilt and flow matched.
New Autolite plugs properly gapped, new Delphi coil, new TFI moudle, new TPS, new cap and rotor button, new MAP sensor, new IAC valve, new Ford spark plug wires new 65amp alternator, new belts, timing set at 10 degrees, new Bosch O2 sensor, new battery, inertia switch bypassed.
New cooling system including radiator, radiator cap, hoses, fan clutch, water pump, thermostat, coolant temperature sensor, coolant and etc.
Throttle body cleaned.
Upper and lower intake cleaned inside and out, new air intake temperature sensor
New EGR pressure sensor and new EGR valve.
K&N air filter
New OEM Walker exhaust system from the converter back.
Stock rebuild from intake to oil pan.

New A4LD built to take a beating, new torque converter with factory stall speed, new B&M Super Cooler trans cooler, the truck came with factory 4:10 gear sets.


Here's the problem, the truck will fire right up and idle like new, quiet and smooth as can be, can and will idle for as long as I want, coolant temp reads normal. Will fire right back up once it is hot just like it left the factory. Checked for codes with my OBD1 scanner, no codes at all. The engine will somewhat rev fairly easily to around 1400-1600rpm then act like it is starving for fuel, I have adjusted the timing and no significant or noticeable change in performance. I checked the FP a the rail from the Schrader valve and it reads around 34-39psi and will slowly fall to around 30psi and hold there. I feel like the FPR is working as it should be. All vacuum lines and sources are good and all seems well with vaccum at this point. I have no idea as to what to try now or where to start running down another potential problem that might me out of sight and out of mind.

Anyone have a clue as to where I need to start or have any advice on what I may be over looking with this new build?

Thanks in advance.

 

Did you put the SPOUT connector back in?
It adds "vacuum advance" spark timing, computer suggested spark advance


Put vacuum gauge on engine
Should be 18-21" at idle on fresh rebuild
Raise RPMs to about 1,500, vacuum should drop a bit then come back up to 18-21" and hold steady, if its dropping then exhaust is clogged up, new or not

Check MAP sensor vacuum line again, its the engine Load sensor, tells computer what fuel mix to use when REVing

Disconnect EGR vacuum hose and plug it, see if it REVs better, could be issue with EGR solenoid(vacuum valve)

The computer is getting timing pulse from TFI module or injectors wouldn't work at all

Don't think TPS could do what you describe, you could try Clear Flooded Engine test to see if its working
Key on engine off
Press gas pedal down to the floor and hold it down all the way
Crank engine over
It should NOT START or even fire, fuel injectors are OFF

Release gas pedal at any time and they will start back up

 

Yes, the SPOUT connector was reinstalled. Thank you for the helpful and detailed reply, I will try all of the above tomorrow night when I get off of work and report my finds.

Thanks again for your reply!

 

Alright, I had a chance to spend some more time on my truck last night and try your advice with my problem. Here is what I can vouch for:

Vacuum gauge shows a consistent 20" of vacuum at idle, I checked this 5 different times and no change.
I pulled the MAP sensor line off and blew through it again with the air hose and it is free flowing as it should be, swapped out the old OEM MAP sensor to a new one, no change at all.
Pulled the vacuum line off the EGR and capped it resulting in no change at all.
I swapped the old TFI module with the old OEM unit resulting in no change at all.
I also swapped the old OEM TPS sensor with a new unit resulting in no change at all.
I preformed the Clear Flooded Engine test, with the pedal fully depressed the engine WILL FIRE right up.

I bought another FPR and replaced the new OEM Bosch unit with a Standard name brand FPR and still no change.
I pulled the high pressure pump off as well as all of the supply and return lines and used the air compressor and blew threw the line to ensure that there is no blockage and no obstructions, done the same for the lines on the tank since the bed is still off of the truck, in tank fuel pump with spray fuel about 2-3 feet with the line unhooked once the key is switched on. The fuel return line was bone dry as well.
I pulled the fuel canister off of the rail and opened it back up to ensure that there was nothing blocking the flow of or the restriction of fuel, nothing but clean fuel on the canister and no blockages or restrictions.

I hooked all of the fuel lines back up, cycled the key off and on 40+ times or more to cycle the pumps to purge the air out of the lines, after this process the fuel pressure still will not hold any PSI over 25-30PSI. I had my dad to continue to cycle the key on and off for a few minutes while while I checked for any visible leaks with the only thing that I noticed is that there appeared to be a very minor trace of fuel leaking from the fuel canister where it would thread on. I plan on removing the canister either tonight or tomorrow and completely sealing it off. Other than that all appears and tests to be operating as it should.

I'm at a loss at this point, I have no idea as to what to try now, if I can't figure out this issue I will purse another vehicle of the same 83-86 range and swap the engine and drive train into that vehicle. I have never had any vehicle to cause me this much problem with a rebuild in my life. Any and all advice will be greatly appreciated.

Thanks in advance.

 

It should not have, if done properly
Turn key to "RUN" position, then fully depress gas pedal and hold pedal to floor, Then turn key from "RUN" to "CRANK" do not turn key to OFF then CRANK.

If it is starting, you either have leaking injectors or a stretched throttle cable.

To test throttle cable, get someone to hold gas pedal fully to the floor, while you check throttle body to see if you can manually open it farther.

 

Just tried it using this method, it WILL NOT start.

 

And how was Vacuum when engine was at 1,500 RPM does it stay steady or slowly drop(partially clogged exhaust)

Swapping engine into another body can't fix an engine issue

 

At 1500rpm it held steady at 20" and never dropped off at all. As of right now the fuel system will only build 19PSI and hold there for about and hour and then start to taper off. Is it possible that somewhere within the fuel system, lines canister that there is a pin hole or something causing cavitation for this system to do what it is currently doing?

On the fuel side of things I have been through 2 new FPR's (OEM and now a Standard) and 2 new high pressure fuel pumps(Delphi) and 0 miles on either and nothing has changed.

I have no idea as to what to try next other than completely removing the fuel lines from the truck and cleaning them and then submerging them in water and pressurizing to them to check or a potential leak or some sort. There is no leak or smell of leaking fuel anywhere on the underside of the truck at the moment.

 

OBD1 connector does have a Fuel Pump Relay by-pass so you can turn on Fuel Pumps full time, well with key on full time
This can help fund/solve fuel pressure issues

Look here: https://www.therangerstation.com/tec...ry/OBD_I.shtml
2nd drawing shows the Fuel Pump slot on connector

If you GROUND that slot then fuel pump relay will activate as soon as key is on, so full time fuel pumps
So jumper to battery negative or near by ground

Do you know for sure if pump in the tank is working?
You can disconnect high pressure pump and then power them up and see if you can hear the lift pump in the tank

 

Well, after a many of long nights when I get home from work and after (2) in tank pumps(Delphi), (2) High pressure pumps(Delphi), (2) fuel pressure regulators(one NOS OEM & one Standard, (2) MAP sensors, (2) IAC valves, (2) TPS sensors, (2) fuel rail gauges and swapping new parts and old parts with new parts we have finally found the problem and I mean we only found the problem by routing the supply line from the low pressure pump side of the fuel hat directly to the high pressure frame rail mounted pump. It cranks, idles and rev's as it should, rail pressure by my gauges read 39psi and when revving the engine the OEM FPR functions as it should. While during the process's of elimination we discovered that the new Standard FPR would fall about 6psi short of where it should be, so I swapped back to the OEM Ford FPR and that's when it hit 39psi and the engine rev'ed as it should. I'm not sure if there is a pin hole or a very small leak or what between the tank and the frame mounted canister, I did remove the canister again and sealed it shut prior to my finding and it did not help at all. But right now, I have never been as happy as I am to have fixed this problem that I have encountered. I most definitely owe a BIG THANK YOU to RON D for all of his detailed help and replies, I did learn a few things with this issue that I will remember for the rest of my life.

Thanks again!

 

Thanks for the thanks, and for the update, it WILL help someone else down the road