Runs better with the fuel pressure regulator disconnected

junkyardjeff · July 04, 2013, 02:21:32 PM

I have a 1988 bronco with a 5.0 that has fuel pressure issues since I bought it so here is some history,it has a two pump system and the pump in the tank was bad so I replaced both pumps,regulator and relay since I dont know how long it was driven with the rear pump bad and it has a bunch of miles on it. In about 6 months the new rear pump went bad so it had to be replaced,the motor always surged a little when firing up but now has to be started twice when cold so I put the pressure gauge on it and is 29 with the motor running and regulator connected and with it disconnected it goes to around 40. With the vacumn line to the regulator disconnected and plugged it stats right up and does not surge and runs better so where do I start on seeing why the pressure is a little low,I want to convert to the 90 and newer single pump system if I can find one in the junkyard to get the parts.

unklian · July 04, 2013, 05:44:20 PM

What is the pressure supposed to be ?

wayne petty · July 04, 2013, 05:55:39 PM

key on.. engine off...

does the pressure come instantly to 39PSI.. or does it take a while to build???

how the fuel pressure regulator controls fuel rail pressure
http://oldfuelinjection.com/?p=41

fuel pump system
http://oldfuelinjection.com/?p=95

how to run a KOEO and then a KOER test... so you know that you get a PASS 11 without any current or memory codes..

http://oldfuelinjection.com/?p=13

i think i recall that you have a snap on MT2500...

post codes.

junkyardjeff · July 04, 2013, 07:17:55 PM

I do not have a manual for the truck but the shop manual for my 89 crown vic says 30 to 45 while running,I will have to see how fast the pressure comes up and report back.

junkyardjeff · July 04, 2013, 08:03:42 PM

It sat all night and the pressure did not go up instantly the first time but after it was started it came up instantly,I did notice the pressure gauge flickering where I dont remember it doing it the last time I checked the pressure.

wayne petty · July 05, 2013, 12:15:05 AM

both pumps run off the same circuit..

disconnect the inlet of the high pressure pump.. and turn on the key.. see if you get a good flow from it...

if you do.. then hook the high pressure pump back up and start the engine... see if its gotten noisy..

you can build a test harness to disconnect one power wire to the external pump.. run it thru the digital volt meter...set at 15 or 20 amp DC.. and measure the amp draw...

should be less than 7 amps with the engine running.

this is kinda how your 88 is wired.. there may be slight differences...

note that the key turns on the Main relay with the red and green stripe wire...

that sends power to the injectors and the ignition coil.. the ignition coil is direct from the switch..

the red wire also sends power to the coil winding of the fuel pump relay... so the computer can control it by pulling it to ground...

the inertia switch is probably in a different location in the wiring on your 88... but this is how it does work..

if you have the key on.. and you jump the #926 terminal on the EEC4 test connector go GROUND.. it will pull the fuel pump relay on and allow you to prime the system .. but also allow you to check the fuel pressure and amp draw without the engine running..

i did not just draw these for you.. i cover 4 ford magazine forums and have to have these handy to cure peoples ills..

since it runs better with more fuel pressure...

i would like you to run a KOEO and a KOER test if you can...

i would also like you.. and i know this is a pain...

check the air injection system for leaks... rusted out tubing.. rusted out check valves... and proper operation of the diverter valve..

the diverter valve assembly gets burned when the check valves fail.. allowing hot exhaust to come back up the air injection pipes.. then the diverter valve allows uncommanded air into the exhaust stream before the oxygen sensor.. when it does this.. it throws off the actual oxygen sensor readings and kills the drivability..

my older sister has an 87 town car with the 5.0 EFI... after i finished working on it... she gets 29 to 32 MPG on the highway with it.. that is the same motor and fuel system thats in your bronco.. she has an advantage... she learned how to drive from a WWII pilot friend of mine.. he taught her how to roll slowly into the throttle and roll out slowly to improve gas mileage.. and for those who have been around.. yes.. the old man with the boat.. that old guy has a DFC for B29 missions over toyko at crazy low altitudes..

junkyardjeff · July 05, 2013, 12:27:30 AM

I will run those tests tomorrow,I do not think there are any bad tubes in the air system but the solenid that controls the vacunn to turn on/off the valve at the air pump is bad so I have it where its pumping it through the system all the time. The noise of the air pump shooting the air out was annoying,the front pump is so noisy that I can feel it vibrate through the steering wheel.

wayne petty · July 05, 2013, 01:20:38 AM

Quote from: "junkyardjeff"I will run those tests tomorrow,I do not think there are any bad tubes in the air system but the solenid that controls the vacunn to turn on/off the valve at the air pump is bad so I have it where its pumping it through the system all the time. The noise of the air pump shooting the air out was annoying,the front pump is so noisy that I can feel it vibrate through the steering wheel.

if its going into the UPSTREAM air.. the tubes into the exhaust manifolds.. or back of the heads... this will dilute your exhaust stream with additional oxygen.. throwing off what the computer thinks the air fuel ratio actually is..

hint... later diverter valves are not a direct fit onto the bracket but do work the same inside.. try one from a 91/92 town car 5.0..

the solenoids...

TAB.

TAD.

EGR..

~~~~~~~~~~~

tab., thermactor air bypass... this dumps air out of the system up at the valve nearest the back of the smog pump..

tad... vacuum not applied... air flows to the upstream ports
vacuum applied.. air goes to the pipe down to the front of the cats or side of the cat.. depending on your cat..

Egr... this PULSES air to the EGR valve to control its opening percentage.. feed back from the EGR position sensor on top lets the ecm know how far its open..

here is the thermactor system section from AZ..

http://www.autozone.com/autozone/repairguides/Ford-Crown-Victoria-Grand-Marquis-1989-1998/Emission-Controls/Thermactor-Air-Injection-System/_/P-0900c152801e4946

i will have to dig around for the TAB/TAD/EGRsol diagnostics.. but they are in your printed manual..

please put a TEE.. in the end of your vacuum gauge so you can move it around to different hoses to check that the vacuum signal is actually getting properly commanded..

warning.. you cannot without a risk of drivability issues.. just disconnect and plug the thermactor system..

when the system goes into self test each time..

when the system/engine is warmed up and the engine above idle speed, the ECM commands the TAD valve to divert air into the upstream exhaust during closed loop.. this is just for a second.. it looks at the changes in oxygen sensor readings to verify the diverter valve is actually working.. if it does not see a change.. it will set a code..

i have forgotten what the 2 or 3 digit code is but its a P0411 on later OBD2 models.. this shows that the diverter is not functioning as directed.. and it could be a worn out or defecting smog pump thats not putting out enough pressure to overcome back pressure in the exhaust

usually TAB/TAD/EGR sol issues are lack of manifold vacuum on the red hose... either its disconnected near the manifold.. or the soft sections have separated or collapsed..

an additional thought.. do not replace rigid nylon tubing on these with rubber hose.. use as much of the rigid nylon tubing as you can.. its actually available in most parts stores if you look around near the PCV valve display.. along with new adaptor ends.. rubber vacuum hose expands and contracts with the pulses of vacuum sent by the solenoids.. this reduces the response from the diverter and egr valves. this .. this is really critical on the EGR...

sorry to bury you in info...

there is a LOT of good reading in your 89 manual.. on the oidfuelinjection site.. and at the autozone site..

you can even give me a call if you want..

junkyardjeff · July 05, 2013, 08:39:13 AM

The smog pump is a little noisy and I think I checked to see if the divertor valve was working last year but I am going to make sure it dumps air to the cat constantly until I can make sure its all working right. I think the tab was getting constant vacumn that made it constantly dump air si I plugged the vacumn line so I might just hook it up and let it dump for the time being.

junkyardjeff · July 05, 2013, 08:35:25 PM

I done those tests and it only came up with insufficient egr flow which I knew it would since the egr is froze up and I know the solenoid does not work,the front fuel pump is getting more noisier so I think that might be where the problem is and will check the flow from it.