Greetings Gents and happy holidays. I'm a noob here , and like most ,I have problems. I have a 92 F150 w/4.9 6cyl flairside,single aft fuel tank, EEC-IV. Truck has been sitting in the garage for years. Fuel pump was bad,so I changed the tank and pump/sender module and filter. I now have a no start situation, but it will start and run on ether/gas /whatever I spray into the TB. New fuel pump works makes 60psi at the fuel rail shrader when I turn the key on, and when I jump the FP test port to ground. Question 1 is: should it hold that pressure for any period of time? (KOEO of course). I checked the FPR and it will hold 20 in/hg pretty much forever. Everything else I ever worked on with FI had a fuel pressure leakdown test, and I dont see mention of it anywhere about the fords. Other issues so far are :I get a very low .036v VREF reading at the TPS and MAP ,but pin 26 (VREF) brn/white at the PCM is 5v (normal). I also get injector pulse with a noid light at the PCM (40 and 60)black/white wires. Not sure if I have pulse at the inectors yet because I'm still trying to get one of the FI plugs off under the plenum w/o breaking it. OK now that I've made this post a mile long...any thoughts? Thanks much -George

 

Sounds like the injectors aren't firing.

Been sitting long enough for a friendly rodent to chew through some wires, maybe?

If you had a mechanic's stethoscope and another pair of hands, then you could listen to the injector(s) while a friend keep spraying some fuel into the TB. If you don't hear any clicking, then that would be a good sign a wire is chewed through or damaged and your not getting signal from the PCM.

You can disconnect the 60-pin PCM harness and then trace the wire back to the 40-pin Square connector on the driver fenderwell. Then disconnect it from the harness leading to the engine. Do a resistance check to see if the wires for the injectors are good. If they are, then next is to check the 40-pin harness running to the engine.

Hope that helps. Others will chime in!!

 

Every time I read this problem and I have seen it on here a lot of times it always turns out to be plugged up injectors.
You will need to pull all the injectors out and clean & rebuilt them or replace them.

Leak down:
About 2lbs in 5 minutes, 5lbs in 2Hrs.
Zero psi over night.

 

where is the 40 pin connector? My starter died on my working on diagnosing/replacing it now. I was going to try to get to a inj plug to make sure what I have over there..is that a test plug I see coming off the FI harness by the fuel rail? Any thoughts on the failure to hold fuel pressure? Thanks so much for your response-George

 

sorry,saw this after my first reply...I was afraid of that too-trucks been sitting for years. I dread tearing the plenum off. I thought maybe an injector could be stuck open causing the rapid leak down..what do you think? Thanks much for your reply...even if it wasnt what I wanted to hear -lol

 

I agree with the above.....you have open circuits and rodents are the number one cause given the previous statement "truck sat for years".

 

You have more than one problem: "Other issues so far are :I get a very low .036v VREF reading at the TPS and MAP ,but pin 26 (VREF) brn/white at the PCM is 5v (normal)."

I agree the injectors may be plugged but you have more to deal with here.

 

I dough the the injectors are causing the leak down. At this point more than likely the fuel pressure regulator.

 

Should not be any open plug by the fuel rail. It needs to be plugged into something.
A photo would help of the plug. Maybe it was for a FI manifold fan.

 

"where is the 40 pin connector?"
It is a 42 Terminal inline plug C101 at the LH side of engine compartment, side of wheel well (E9) in image below.

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Just for grins and giggles, I suggest that you check the fuel pump relay. it is under the hood on the drivers side. I had the same problem and that worked for me.

 

if I am getting a good vacuum hold on the FPR could it still be bad?

 

I dont see any physical signs of chewing. I just got my starter back in after a rebuild, so I can get back to a few test. I would love to see an injector pulse at the injectors before I tear this plenum off. Is that just a single tab on the top of those plugs? If so I may be able to wiggle on off for testing.

 

Thanks much to everyone for all the suggestions/advice. With these 4.9 plenums,other than the obvious bolts to the lower intake,is there just the bracket under the EGR that holds them on? I assume the throttle body can be pulled with it as a unit? I have a haynes manual here ,and if theres a good description,I cant find it. Thanx again

 

Here is what the 1992 shop manual says:
Manifolds

Removal

1. Disconnect the inlet air hose at the crankcase filter cap. Remove the throttle body inlet hoses.

2. Disconnect the accelerator cable at the throttle body. Remove the cable retracting spring. Remove the accelerator cable bracket from the upper intake manifold and position the cable and bracket assembly out of the way.

3. Remove the fuel line from the fuel rail. Do not bend the fuel line.

4. Remove the upper intake and throttle body assembly.

5. Disconnect all the vacuum lines. Label the lines so they are re-installed properly.

6. Disconnect the inlet pipe from the exhaust manifolds.

7. Disconnect the power brake vacuum line (if so equipped).

8. Remove the bolts attaching the manifolds to the cylinder head. Lift the manifolds from the engine. Remove and discard the gaskets.


Installation

1. Clean the mating surfaces of the cylinder head and manifolds.

2. If one of the manifolds is to be replaced, remove the tube fittings from the discarded manifolds and install them in the new manifold as required. Also install new studs in the new manifold.

3. Install a new intake manifold gasket.

NOTE:
Combination intake/exhaust gasket is not to be used on a new exhaust manifold. Gasketing of the exhaust manifold is only recommended when the original exhaust manifold is reinstalled, in order to prevent leakage.

4. Coat the mating surfaces lightly with Steering Gear Grease C3AZ-19578-A (ESW-M1C87-A) or equivalent graphite grease. Place the manifold assemblies in position against the cylinder head. Make sure that the gasket has not become dislodged. Install the attaching washers, bolts and nuts. Tighten the bolts and nuts on intake manifold to 30-43 N-m (22-32 ft-lb) and on exhaust manifold to 30-43 N-m (22-32 ft-lb) in the sequence shown.

5. Connect the inlet pipe to the exhaust manifold. Tighten the nuts to specifications.

6. Connect the crankcase vent hose to the intake manifold and position the hose clamp.

7. Install the upper intake and throttle body assembly using new gaskets.

8. Install the exhaust manifold-to-muffler inlet pipe lockwashers and nuts. Tighten the nuts to specification. Refer to «Section 09-00», Exhaust Pipes, Mufflers and Converters.

9. Connect the engine ground strap and the battery ground cable.

10. Connect Electronic Engine Control (EEC) harness to all sensors.

11. On a vehicle with an automatic transmission, connect the kickdown cable to the throttle body.

Connect the accelerator linkage to the throttle body and install the retracting spring.

On a vehicle with power brakes, connect the brake vacuum line to the intake manifold.

12. Connect the coil primary wire, RFI capacitor (on coil bracket), oil pressure and coolant temperature sending unit wires, flexible fuel line, heater hoses and the battery positive cable.

13. Install the alternator on the mounting bracket.

Install the power steering pump on the mounting brackets.

14. Install the water pump pulley, viscous fan drive (right-hand threads on fan clutch), cooling fan and drive belt. Tighten the fan bolts to 16.2-24.4 N-m (12-18 ft-lb).

Tighten the alternator, power steering pump and air pump and air compressor mounting bolts to specification. Refer to «Section 03-05», Engine Accessory Drive.

15. Install the radiator. Connect the radiator lower hose to the water pump and the radiator upper hose to the coolant outlet housing. Connect the air compressor lines. If removed, install air conditioner compressor and condenser.

On a vehicle with an automatic transmission, connect the oil cooler lines.

16. If applicable, install and adjust the hood.

17. Fill and bleed the cooling system. Refer to «Section 03-03», Engine Cooling. Fill the crankcase. Operate the engine at fast idle and check all hose connections and gaskets for leaks.

18. Perform EEC Quick Test to check the function of the EEC system. Refer to «Powertrain Control/Emissions Diagnosis Manual» .

19. On a vehicle with manual transmission, check for correct clutch operation.

On a vehicle with an automatic transmission, adjust the transmission control linkage. Refer to «Section 07-05», Shift Controls, Automatic Transmission. Check the fluid level and add as required to bring it to the proper level on the oil indicator.

20. Install the throttle body intake tubes.