Fuel Pump Maybe? 4.9L fuel injection 1990

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New member
Aug 30, 2010
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Actually, this engine is not in a Bronco, but it's a 4.9L fuel injected 1990, so I thought you guys may know something.

1990 Ford f150 pickup truck with a 4.9L fuel injected 6 cylinder engine.,

I'm at a loss now. I don't know the history because the person giving me the truck doesn't know either. I did some work that's not relevant here. I changed the fuel pump with a junkyard one. It took a lot of work, particularly removing the one in the junkyard.

Now I need to get it running properly. I can't get it to respond the the throttle. that is, when I get it to start, it's hard to "gun" the engine; in may cough and die.

I tried the self test (http://fordfuelinjection.com/?p=13 self-test, with "ST in" grounded ) and with the engine off (KOEO) I got 556 meaning fuel pump circuit. I didn't do the test while the engine running because I don't know how then. I just learned you start the engine first then ground st1, then look at the codes.

And I don't know where the fuel rail is or the Schrader valve to do a fuel pump pressure test. Anybody have a diagram? Or can someone just tell me? It must be simple to find, but I'm not sure I located it yet.

And what's my next step? Do I test the fuel pressure?

Any suggestions at all will be appreciated.

~~ Nehmo



96 Bronco 5.0
Staff member
Oct 18, 2005
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Floating in the Pacific

good work K

Also, read thru this TSB; btw, need to know your Calibration number from your B-pillar sticker

Fuel Pressure Regulator (FPR) Delay TSB 93-22-14 for 90-93 4.9L (Cold Start & Idle Stall)

Source: by Ford via miesk5 @ http://home.comcast.net/~miesk5/technical_service_bulletins.htm#technical_service_bulletins.htm

TSB 93-22-14 4.9L Stall on Initial Start-Up

Publication Date: OCTOBER 27, 1993


1990-1993 BRONCO, ECONOLINE, F-150-350 SERIES


0-51R-R00, 0-51R-R02, 0-51F-R00, 0-51F-R02, 0-51H-R00, 0-51H-R02, 0-51G-R00, 0-51G-R02, 0-51E-R00, 0-51E-R02, 0-52L-R00, 0-52L-R02, 0-52R-R00, 0-52R-R02, 0-52S-R00, 0-52S-R02, 0-52Q-R00, 0-52Q-R02, 0-52K-R00, 0-52K-R01, 0-52K-R10, 0-52J-R00, 0-52J-R01, 0-52H-R00, 0-71J-R00, 0-71J-R01, 0-71J-R02, 0-72J-R00, 0-72J-R02, 1-51R-R00, 1-51F-R00, 1-51H-R00, 1-51G-R00, 1-51E-R00, 1-52L-R00, 1-52R-R00, 1-52S-R00, 1-52Q-R00, 1-52K-R00, 1-52J-R00, 1-52H-R00, 1-71J-R00, 1-72J-R00, 2-51R-R00, 2-51F-R00, 3-51F-R00, 2-51H-R00, 2-51G-R00, 2-51E-R00, 2-52L-R00, 2-52R-R00, 2-52S-R00, 2-52Q-R00, 2-52K-R00, 2-52J-R00, 2-52H-R00, 1-71J-R10, 1-72J-R10, 2-72M-R00


ISSUE: A stall may occur in NEUTRAL or PARK on initial start-up, within 15 seconds, as the engine RPM is coming off fast idle. This occurs because of insufficient fuel pressure on the cold start.

ACTION: Install a ported vacuum switch in the heater inlet hose to delay vacuum to the fuel pressure regulator and boost fuel pressure. Refer to the following procedure for service details.


1. Confirm that the vehicle has been properly maintained. Verify a pass code 11 or 111 in EEC IV Self Test.

2. Confirm no other concerns are present such as ignition, fuel pressure, air intake, exhaust, etc. After all these areas have been checked and no other concerns exist, then proceed to Step 3.

3. Install an 85� F (29� C) ported vacuum switch (D5VY-9D473- B) in the heater inlet hose to delay vacuum to the fuel pressure regulator, boosting fuel pressure about 10 PSI on the cold start.

a. Cut the heater inlet hose about 12" (305 mm) from the inlet tube on the the thermostat housing.

b. Install tee assembly (F2TZ-18B402-A) and clamp both sides. Install switch into truck.

c. Install a 12" (305 mm) piece of 5/32" (4mm) vacuum hose to the lower fitting (labeled S) of the ported vacuum switch. Using a vacuum elbow fitting (387065-S), connect it to the red vacuum line that goes to the fuel pressure regulator.

d. Add another 12" (305 mm) piece of 5/32" (4mm) vacuum hose to the top fitting (labeled E) of the ported vacuum switch. Connect it to the fuel pressure regulator.

4. Install a fuel pressure gauge and verify that the fuel pressure drops about 10 PSI, at idle, when the engine temperature nears 85� F (29� C).

Obtain an Authorized Modifications Decal and list the date, dealer number, and summary of alterations performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.


D5VY-9D473-B Ported Vacuum Switch

F2TZ-18B402-A Tee Fitting

387065-S Elbow Fitting (Pk./2)

Obtain Locally Vacuum Hose - 5/32"

OTHER APPLICABLE ARTICLES: 91-22-8 , 92-12-17 , 92-18-11 , 92-9-13



DESCRIPTION Perform EEC IV Quick Test, Install PVS

TIME 0.9 Hr.

see Link for the Images if the Zone won't allow it them appear;





Next is 300 (4.9L) Parts Break-Out Diagram,49lexploded.jpg

by Steve83


see the Fuel Rail & Fuel Pressure Regulator (FPR) on passenger side


556 (O,M) Fuel pump relay primary circuit fault -

You will need to trouble shoot the circuit to see if it is a EEC or FP relay, the inertia switch or corroded wiring, relay sockets, etc.

The fuel pressure should be in the 45-60 psi range.

The pump normally runs a couple seconds when the ignition is in Run (not start) position. Listen for it


will try to bbl w/wiring diagrams, so far, I don't have any Links to one in my site.



96 Bronco 5.0
Staff member
Oct 18, 2005
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Floating in the Pacific

Let's try that KOER test now before we begin to go nutz over reading the wiring diagram way down below.

SELF TEST - COMPREHENSIVE & Connector Location pics, Bronco & Ford; "...The self-test plugs were mounted on the passenger side fender on 1985-86 EFI trucks; The self-test plugs are located along the driver's side fender behind the air filter box on 87-95 EFI trucks..."; miesk5 NOTE; Self-Test Output (STO) is the Pin in the Lt gray Connector and Signal Return Ground (SIGRET) is Pin E in black Connector in 87-95; The engine temperature must be greater than 50°F (10°C) to pass the KOEO Self-Test and greater than 180°F (82°C) to pass the KOER Self-Test. Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accesories/lights, etc. Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch. Do Key On Engine Off (KOEO) portion first. Look Codes up in my broncolinks.com site using the new Search function. or post em here again and sepcify it they are KOER or KOEO.

Source: by our buddy, BroncoJoe19 (Joe) at http://broncozone.com/forums/index.php?showtopic=14269&st=0

let's inspect the fuel pump relay and it's socket and the wiring that you can see; when engine is @ normal operating temperature the FP/and/or EEC relay can fail for heat-related issues; the engine will thus be fuel starved, and stop.

Socket Corrosion Info; "...if you had corrosion in your relay socket, then you probably have it other places. one at a time unplug all relays and connectors on that fender and spray them down with contact cleaner. then after you let that do it's job for about 30min-1hr, go back and unplug each relay and connector again (one at a time) this time put them together with di-electric grease. you can buy a tube of it from any electrical/electronics supply or auto store. make sure you get everything plugged back in..."

Source: by datrimm (HiTechRedNeck)

Operational Sequence; "...

When the ignition switch is ON, it turns the EEC power relay ON.

The EEC power relay provides power to the powertrain control module (PCM) and the control side of the fuel pump relay when it senses rotation in the dizzy from the pickup

Power for the fuel pump(s) is supplied through a fuse link or high current fuse attached to the starter solenoid (battery side). From the fuse link or high current fuse, current flows through the fuel pump relay and inertia switch to the fuel pump(s).

When the ignition switch is turned ON, the fuel pump(s) will operate.

If the ignition switch is not turned to the START position the PCM will shut the fuel pump(s) OFF after 1 or 2...seconds.

The PCM will operate the fuel pump(s) when the ignition switch is turn to START position to provide fuel while cranking. After the engine starts, the PCM will continue to operate the fuel pump(s) unless the engine stops, drops below 120 rpm

or the inertia switch is tripped...is used as a safety device in the fuel system. The inertia switch is located in the cab, generally under the dashboard on the right side. It is designed to open the fuel pump power circuit in the event of a collision. The switch is reset by pushing each of 2 buttons on the switch simultaneously (some models use switches with only one reset button).

The inertia switch should not be reset until the fuel system has been inspected for damage or leaks." (under license from Delmar Publishers, combo of Chilton/Nichols/Delmar & Haynes); some may be incorrect, as reported by Seabronc, thanks Seabronc! NEW SITE URL!!! MUST REGISTER TO VIEW; select year, make, model, engine size and go to appropriate section http://www.autozone.com

You should test your relays by applying 12 V across the small terminals, listen for the click and check continuity across the large terminals. This will rule out the relays themselves being a problem. Usually they ARE the problem, so hopefully you can stop there. They absolutely HATE moisture so if you are missing your cover Im sure some moisture got inside the relays themselves. The pickup in the distributor can throw a code when it is intermittent or not working. One of many reasons you should check your codes..."

Source: by kf4amu (Will H, The Beast

Color Codes for Troubleshooting/Swapping to Bosch Style Relays

Source: by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/507189

Bosch Overview, Schematics, etc.

Source: by Craig U at http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm


EEC IV Pin-Outs in 88-89 & 90-91 Bronco 4.9; 88-90, 91 & 92-93 Bronco 5.0; 88-91 & 92-93 Bronco 5.8; Looking Into Harness Connectors in Ford Electronic Engine Control Overview, Chapter 12, Ford Fuel Injection and Electronic Engine Control: How to Understand, Service and Modify, 1988-1993; & Ford Fuel Injection and Electronic Engine Control: How to Understand, Service, and Modify All Ford-Lincoln-Mercury Cars and Light Trucks, 1980 to 1987 by Charles Probst


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