Runs better with fuel pressure regulator vacumn line plugged

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Jeff Ogden

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I have been fighting fuel pressure issues since I bought this 88 with a 5.0 so here is the history,the pump in the tank was bad so since I had no idea on  how long it was driven with the rear pump out I replaced both.    About 6 months after installing the rear pump it went bad and was replaced,the motor always surged a little for a few seconds after starting but got hard th start when cold so I put the pressure gauge on it and this is what I have found.     29 with the regulator hooked up and motor running and 40 with the regulator unhooked and when shut off the pressure does not instanly drop,I have no specs for this truck but the shop manual for my 89 crown vic says 30 to 45 with motor running so it looks like I am on the edge of having ow fuel pressure if its about the same.  Where do I start looking.

 

miesk5

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yo JEFF,

I have some possible checks below incl Ford's Fuel Pressures for your 88 5.0; but first,

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

http://broncozone.com/topic/14269-code-reader/?&pid=74587&mode=threaded
 

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.
Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/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.

And Post em here according to:
KOEO
&
KOER
 

Joe includes a vacuum check, so do that too

I have a vac leak test at http://broncozone.com/topic/22770-low-idle/

Fuel Pressure Specifications TSB 88-03-13 for 88 Bronco & F Series

FUEL PRESSURE ENGINE RUNNING 30-45 PSI  KEY ON, ENGINE OFF 35-45 PSI  by Ford

Maximum fuel pressure is obtainable at WOT or the vacuum hose removed from the fuel pressure regulator

After attaching the fuel pressure tester, run the fuel pump for 10 seconds. Check that the pressure is within specs, and it doesn’t leakdown more than 5PSI within 60 seconds after pump shutdown.
 

Pull vacuum line off  Fuel pressure regulator; any gas or aroma of gas, indicates diaphram has ruptured, R&R FPR

Single-Function Reservoir Testing in 88-89; "...Used on 88-89 Broncos & F-series/E-series/Rangers/others with single tank dual-pump EFI. In this version, the only moving part is the tank-side inlet check valve. The return ports flow freely and are NOT connected to the reservoir. The engine-side supply port is open to the reservoir.

To test it, unplug the frame fuel pump, disconnect the engine-side supply (large) line, and cycle the key. If fuel flows out of the reservoir ******, the reservoir is working normally. If not, disconnect the tank-side supply (large) line, and cycle the key. If fuel flows out of the line, the reservoir check valve is probably stuck, or its internal filter is clogged

EFI Engines
CAUTION: Fuel supply lines on 4.9L EFI, 5.0L EFI, 5.8L EFI and 7.5L EFI engines will remain pressurized for some period of time after the engine is shut off. This pressure must be relieved before servicing of the fuel system.

Before opening the fuel system on vehicles with EFI engines, relieve fuel pressure as follows:
1. Locate and disconnect the electrical connection to either the fuel pump relay, the inertia switch or the in-line high pressure fuel pump.
2. Crank engine for approximately ten seconds.
NOTE: Engine may start and run for a short time. If so, crank engine an additional five seconds after engine stalls.
3. Connect the electrical connector that was disconnected in Step 1.
4. Disconnect battery ground cable.
5. Raise vehicle on hoist. Refer to the appropriate model year Volume F, Pre-Delivery Shop Manual, Section 50-04, Hoisting and Jacking.

 

84925062.gif


Fig. 1: Fuel pressure regulator — 5.0L and 5.8L engines

  1. Relieve the fuel system pressure.
  2. Disconnect the vacuum line at the regulator.
  3. Remove the 3 Allen screws from the regulator housing. NOTE: In some cases the factory bent the fuel line over one of the 3 Allen screws making it difficult to remove with an Allen wrench. A pair of pliers may have to be used to break the ***** loose so it can be unthreaded by hand.
  4. Remove the regulator.
  5. Inspect the regulator O-ring for signs of deterioration or damage. Discard the gasket. To install:
  6. Lubricate the O-ring with clean engine oil ONLY!
  7. Make sure that the mounting surfaces are clean.
  8. Using a new gasket, install the regulator. Tighten the retaining screws to 40 inch lbs. (4.5 Nm).
  9. Connect the vacuum line.

Remove the Allen screws — note the fuel line fitting blocking access to the *****

 Once the screws are removed, disengage the fuel pressure regulator from the fuel rail

Check the condition of the O-ring and replace if it is deteriorated or cracked

 Discard the gasket and replace it with a new one

========

FSA 89S76 Cold Fuel Line Leak
Check the Ford website to see if your VIN is affected.
fsa89s76fuelline.jpg
ISSUE: Ford Motor Company of Canada, Limited (Ford) has determined that certain 1986, 1987, 1988 and 1989 model F-150/250/350 Trucks and Broncos sold in specific areas of Canada where severe winter weather is experienced contain a fuel tube that may develop a leak.

Technical Instructions: The new stainless steel reinforced Teflon� fuel line replaces both the short "jumper" fuel line from the high-pressure frame-mounted fuel pump to the filter, and the long fuel line from the filter to the fuel rail on the engine. The existing In-Line Fuel Filter will be removed and discarded. A canister-type Fuel Filter will be added to the existing fuel reservoir on the frame rail behind the high pressure pump.
NOTE: The frame mounted fuel filter was repositioned to between the fuel pump and engine during 1986 model year production. This was incorporated in February, 1986.

Fuel System Pressure Relief

EFI Engines
CAUTION: Fuel supply lines on 4.9L EFI, 5.0L EFI, 5.8L EFI and 7.5L EFI engines will remain pressurized for some period of time after the engine is shut off. This pressure must be relieved before servicing of the fuel system.

Before opening the fuel system on vehicles with EFI engines, relieve fuel pressure as follows:
1. Locate and disconnect the electrical connection to either the fuel pump relay, the inertia switch or the in-line high pressure fuel pump.
2. Crank engine for approximately ten seconds.
NOTE: Engine may start and run for a short time. If so, crank engine an additional five seconds after engine stalls.
3. Connect the electrical connector that was disconnected in Step 1.
4. Disconnect battery ground cable.
5. Raise vehicle on hoist. Refer to the appropriate model year Volume F, Pre-Delivery Shop Manual, Section 50-04, Hoisting and Jacking.

Canister-Type Fuel Filter Installation

CAUTION: If the fuel filter canister is being serviced with the rear of the truck higher than the front, or if the tank is pressurized, fuel leakage or siphoning from the tank fuel lines could occur. To prevent this condition, maintain the vehicle front end at or above the level of the rear of vehicle. Also, relieve tank pressure by loosening the fuel fill cap. Cap should be retightened after pressure is relieved. If vehicle is warm, install the fuel filter before the pressure rebuilds.
1. Remove the reservoir shield on 4 x 4 vehicles by removing either three or four screws (depending on vehicle). On 4 x 4 vehicles it may be necessary to disconnect the rear of the front driveshaft to allow for tool clearance.
NOTE: To maintain driveshaft balance, mark the rear slip yoke in relation to the transfer case yoke for correct positioning during reinstallation. Then remove the nuts and U-bolts (bolts for F350 transfer case) that connect the front driveshaft to the rear slip yoke of the transfer case.
2. Unscrew the lower canister of the reservoir using a flexible strap type oil filter wrench, and slide canister out from frame rail.
NOTE: Fuel canister will be full of fuel.
3. Empty fuel from the fuel canister. Remove and discard the O-ring.
4. Remove the stand pipe from the reservoir by pulling it down sharply. Discard the stand pipe.
5. Install grommet (supplied with filter) into top of filter cartridge, then install the fuel filter cartridge into fuel canister.
6. Position new O-ring so that it is seated in the O-ring groove of the canister.
7. While keeping canister level, so as not to dislodge O-ring, position canister to bottom of reservoir housing and tighten loosely by hand. It may be necessary to loosen reservoir-to-frame mounting bolts to access the canister. Using a flexible strap type oil filter wrench, complete filter canister tightening by turning canister about one-sixth of a turn past initial O-ring compression.
NOTE: The rubber grommet on the filter will automatically seat on the piloted stud of the upper housing as the canister is tightened.
REMINDER: If reservoir-to-frame mounting bolts were loosened in above step, re-tighten.

Fuel Line Replacement:

CAUTION: Fuel lines may still contain fuel. Use caution when disconnecting.
1. Remove the three bolts holding the fuel filter bracket to the frame. Retain one bolt for subsequent use.
2. Disconnect "Push Connect" fitting at the high pressure pump outlet ****** by removing hairpin clip and twisting the line while pulling on it.
3. Using a 16 mm wrench for the fitting and a 14 mm wrench (on the boss of the fuel pump) for backup, unscrew outlet ****** from the front of the high pressure fuel pump. Discard ****** and copper sealing washer.
4. Install new copper washer (E6TZ-9374-A) on the new fuel pump ****** (E6TZ-9416-A). ***** this new ****** into the pump. Torque to 12-16 Nm (9-12 lb-ft), while keeping a 14 mm wrench (on the boss of the fuel pump) for backup.
5. Select the appropriate new fuel line as per Parts Ordering Information.
6. Remove red shipping plug on fuel pump outlet connector of the fuel line if present. Leave white shipping plug on for protection. Install the end of the fuel line with the small bell-shaped connector to the new fuel pump outlet ******. Push on to ****** until distinct click is heard or felt. Pull on line to test for and confirm retention. Engage the retainer clip to line and ****** by firmly pushing down on the clip.
NOTE: If fuel line removal is required use tool T90T-9550-B to release connector.
7. Route fuel line forward inside frame rail, following routing of fuel return line. Install clip N800558-S100 to retain fuel lines, by bolting to lower front bolt hole in frame, that was previously used for the fuel filter bracket. Use bolt from Step 1 and nut N620480-S100. Torque to 8-12 Nm (6-9 lbs. ft.) Ensure fuel line is pressed against frame rail web to clear automatic transmission shift linkage.
8. Disconnect the fuel supply line at the engine fuel rail as follows:
a) lift the tethered retaining clip off the coupling connection. Move it aside, leaving it hanging by its tether.
cool.gif
disconnect the fuel line spring lock coupling, using the proper special service tool.
9. 5.0L or 4.9L engines equipped vehicles. Remove the complete fuel supply line, filter and jumper fuel line as an assembly. Mutilate and scrap.
10. 5.8L or 7.5L engine equipped vehicles. Use a pair of diagonal side cutters to cut both ends of the fuel supply line flush with the foil insulation wrapping. This leaves the wrapped section of the original supply line in place, which is not to be disturbed. Use caution to avoid damaging fuel return line. Mutilate and scrap the ends of fuel lines, fuel filter and bracket and "jumper" fuel line.
11. Remove white shipping cap and connect fuel line to engine fuel rail. Install retainer clip previously removed in Step 8.
12. (5.0L or 4.9L) Strap new fuel line to existing fuel return line using tie straps 95874-S at 8" (20cm) intervals. Cut off excess tie strap length.
13. (5.8L or 7.5L) Strap new fuel line to existing fuel line insulation bundle. Locate tie straps 95874-S at 8" (20 cm) intervals. Ensure heat shield is installed as shown. Use additional strap to secure fuel line to shield. Cut off excess tie strap length. Slight excess fuel line length is allowed to form a "****" at the upper end of the fuel line near the engine.
14. Lower vehicle.
15. Reconnect battery ground cable.
16. Cycle ignition key to "ON" position 5 times at 2 second intervals to prime the fuel system. Inspect reservoir, pump ****** and fuel line connections for leaks (correct as required).
17. Start engine and reinspect the fuel system for leaks. (Correct as required).
18. (4 X 4 only) Reinstall fuel reservoir shield. Torque attaching bolts to 16-20 Nm (12-15 lb-ft).
19. (4 x 4 only) Reinstall driveshaft, if removed, making sure markings on rear slip yoke and transfer casing yoke line up so as to maintain driveshaft balance.
20. Mutilate and scrap all removed parts.

This Recall Supersedes and Replaces Safety Recall 88S57

Recall Time Limitation
None

Parts Return
No

LABOR ALLOWANCES
LABOR TIME: Install new fuel line from the high-pressure frame-mounted fuel pump to the engine and install filter in frame mounted reservoir 1.5 Hrs.
Administrative allowance 0.1 Hrs.
LABOR CODE: B
 

 

Rons beast

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Hey Jeff,

If the fuel pressure goes up when ther vac line is removed the regulator is doing what it is supposed to do.

Having the truck run better when the vac line is removed is an indicator the injectors are worn or dirty. ( they allow more fuel with each spray) You can try some fuel system cleaner, it may or may not work. The reactive magnets and pintles could just be weak.

There was a company I found on EBay that sold rebuilt matched sets for under $300. had a good guarantee too.

Good Luck

 
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Jeff Ogden

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Fiter was replaced wen the pumps were replaced and have about 4000 miles on them,the motor has about 180,000 miles

 

Rons beast

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Hey Jeff,

that's about the same milage as The Beast,  he's ready for new/ rebuilt injectors.  I got everything set at optium specs, and still have a slight hesitation and low power on excelleration...timing is spot on and compression good, no codes....plenum and throtlebody clean, valves cleaned..seafoamed....only thing is injectors...just plain worn out..... think I'm gonna order a set soon. 

Good Luck

 
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Jeff Ogden

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I got all the parts to convert to the single in tank pump system and if it ever stays warm will start tearing it apart,considering getting rid of the 33 gallon tank and going with the truck rear 19 galon tank.

 
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Jeff Ogden

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Just changed the oil and it smelled a little gassy so I wonder if it could be the injectors,I am going to change to a single pump system first since the tank pump is getting a little more louder and probably on the way out. Now the question 19 gallon tank or a new 30 gallon since the 90 pump will not fit mine.

 
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Jeff Ogden

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I done the single pump conversion and the fuel pressure is the same so I will have to look into the injectors,I am going to change the pump since its used and I think it could be part of the problem as I have been driving it for a couple months with the pressure hose not clipped in and it did not instantly blow it off.

 

miesk5

96 Bronco 5.0
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yo Jeff,

Maximum fuel pressure is obtainable at WOT or the vacuum hose removed from the fuel pressure regulator.

See if you can hook up the FP gauge up to line before filter and ck psi.. if ok, do same after filter

here is a diy adapter

FP gauge test at fuel filter.jpg

of course, be careful, wok on cold engine..wrap rags around any adaper..etc.

 
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Jeff Ogden

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The used 90 pump was weak,the sending unit quit working about 2 months after installing so I picked up a new sending unit and pump and runs good now and have the regulator hooked up again. I had put the wrong clip in the presure line and did not click all the way in but I was able to drive it for a month before it started leaking so that told me the pump was weak.

 

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