Fuel pump working 40 psi on rail no start

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jimbronco91

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1991 5.0 Custom 5spd started acting missing rough idle and now cranks no start. Replaced fuel pump, fuel filter, injectors, fuel pump fuse. I have 35 lbs of pressure at the rails. Starts with starting fluid but dies. I am lost. Oh by the way I fixed the gas gauge not working by replacing the float when I changed the fuel pump the old float had a pin hole. Any help would be truly appreciated.
 

miesk5

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Yo JIM,
Welcome to our Bronco site!
Below info is from this 91 Engine Service Manual @ 1991 Ford Truck Service Manuals - Google Drive
On pop-up, click "Drive"
It's the file on left side. The other file is frozen.

In attachments See B3


The 91 Electrical Shop Manual has been removed by Google that states
Google Drive can't scan this file for viruses.

1991 Ford Truck Body, Chassis Electrical Shop Manual that is slow to load @

View attachment 219154
View attachment 219249


91 Bronco Dealer Brochure by Ford via via Dezo's Garage @

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf via member BroncMom!

See my mostly recovered site by member schwim @ Ford Bronco And F-150 Links - FORD BRONCO
It contains boo-koo component repairs, installation & parts sources.
 

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jimbronco91

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Yo JIM,
Welcome to our Bronco site!
Below info isv from this 91 Engine Service Manual @ 1991 Ford Truck Service Manuals - Google Drive
On pop-up, click "Drive"
It's the file on left side. The other file is frozen.


The 91 Electrical Shop Manual has been removed by Google that states
Google Drive can't scan this file for viruses.

1991 Ford Truck Body, Chassis Electrical Shop Manual that is slow to load @

View attachment 219154
View attachment 219249

91 Bronco Dealer Brochure by Ford via via Dezo's Garage @

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf via member BroncMom!

See my mostly recovered site by member schwim @ Ford Bronco And F-150 Links - FORD BRONCO
It contains boo-koo component repairs, installation & parts sources.
You have helped me before & thank you for getting back to me so quick. I was hoping for an easy fix buy nothing is easy especially first generation OBD. Thanks.
 

miesk5

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Jim,
Sorry,I
I read with bad vision again today and thought I saw 3.5 pressure!!!
Try a Self Test for Diagnostic Trouble Codes (DTC)s similar to this by my pal, BroncoJoe19?
Excerpt, "...Shut off all electrical accessories or disconnect them (radio, CB's, lighting, etc.).
Turn her off.
Wait ten seconds
Put the jumper wire as indicated between "Self Test Input" and "Signal Return""
post-9476-1209780173_thumb.jpg


⁶⁶Smell around the PCM. If it smells like dead fish, it's bad. Look for leaking capacitors, burned circuits, brown burn marks on or near them.
See Leaking Capacitors by @jowens1126 @ https://www.fullsizebronco.com/forum/7-1980-96-bronco-tech/294553-swapped-eec-no-more-codes.html
Here are some PCM KILLER perpetrators and other causes:
Bad Intel 8061 chip or bad Intel 8361 memory chip
Bad Internal Voltage Regulator, see http://www.fuelinjectedford.com/images/eec085.gif by Ryan M
Burned PCM printed circuit board circuits (brown burn marks).
Water damage from cowl leaks, ESPECIALLY if you you have wet carpet or mat near driver kick panel;
or on PCM Connector due to a bad hood seal near cowl panel, viewable with hood up.
The alternator could be generating an AC voltage spdike due to bad diode(s),
Bronco was jump started on reverse polarity.
Overheated PCM.
 

miesk5

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One more:
An EGR valve that is stuck open at idle can have the same effect as a vacuum leak. So too can the wrong PCV valve (one that flows too much air for the application), or a loose PCV hose. The rough idle in these cases is caused by "lean misfire." The fuel mixture is too lean to ignite reliably so it often misfires and fails to ignite at all. Lean misfire will show up as elevated hydrocarbon (HC) readings in the exhaust, enough, in fact, to cause a vehicle to fail an emissions test
 

Motech

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You say it starts with fluid?

Try disconnecting the electrical connector on your MAP sensor up on passenger side firewall. If it starts then, replace MAP sensor.

(When they go bad, they will often tell the computer that you're at 20,000 feet of elevation, and the computer trims back so much fuel it will never start)
 
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jimbronco91

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You say it starts with fluid?

Try disconnecting the electrical connector on your MAP sensor up on passenger side firewall. If it starts then, replace MAP sensor.

(When they go bad, they will often tell the computer that you're at 20,000 feet of elevation, and the computer trims back so much fuel it will never start)
That was the MAP sensor as soon as disconnected it started right up. Thank you to everyone who replied. My Bronco will be back on the road tomorrow.
 
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jimbronco91

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I replaced the MAP Sensor as suggested the Bronco started right up & ran like a top. The next day it starts great went to get gas & then to the drug store. I went out to start it after returning from shopping & it cranked but no start. I left it where it was & came back the next day with tools, got in & it started. Once again I am stumped & reaching out for help.
 

Motech

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I went out to start it after returning from shopping & it cranked but no start. I left it where it was & came back the next day with tools, got in & it started.

This is consistent with a few old EEV IV pattern failures:

1 • PIP Sensor (aka pickup coil or crank position sensor in distributor)
2 • EEC Power Relay
3 • Fuel Pump

Check Engine light (MIL) is big clue for 1 and 2

Check following when it won't start:

1 • MIL on with key on, then goes off after a few seconds, then comes on solid while cranking is a sure sign of PIP failure. This won't always set a code, and in fact rarely does, but you can test it by disconnecting the SPOUT connector (timing) and cranking it again. If the light stays off cranking, if it starts up, or even if it tries to start better than before, then it's your PIP sensor
2 • If no MIL when you turn the key on, it is probably your EEC Power Relay. Learn where it lives (probably near your diagnostic connector by the left inner fender), turn your key on and whack it with your pocket knife handle. If that wakes it up, you'll hear some clicking and buzzes and your engine should start again.

On the fuel pump, it's not quite as common, but sometimes when they begin to fail, one of the commutators will short out. If the fuel pump happens to stop spinning right on that particular commentator, it will not spin up when energized. I doubt that's your case though, because then it would start and die once or twice before you get a complete cranking no-start, but it is worth a shot if the first two don't apply. Listen for your pump to prime when you turn your key on. If you're not hearing that, then you'll want to listen for the fuel pump relay to click. It is right up there next to that EEC Power Relay. When you turn the key on, the power relay will click once, and the fuel pump relay will click twice, on then off one second later. If you're hearing those clicks, and you're not hearing your fuel pump prime, have somebody crank the engine while you kick the bottom of the fuel tank right where the pump lives. If that fires it up, then you've got a worn pump.
 
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jimbronco91

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I replaced the fuel pump & filter. It was crank no start. Then I replaced the EEC relay. I replaced the EGR & Pipe, injectors, throttle position & I don't remember the names of the rest. I was throwing on parts. Once I followed your suggestion it ran like a champ & then the problem I posted.
 

Motech

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Once I followed your suggestion it ran like a champ & then the problem I posted.

Again, but brevitized:

Check Engine light is big clue.

When it is not starting, watch your Check Engine light.
  • If it comes on with the key on, your EEC Power Relay is working
  • If it comes on while cranking, the PCM is not receiving the PIP signal
Those are the two biggest (and easiest) diagnostic tells for an EEC IV cranking no-start.

Check Engine light is big clue when it's not starting, and if it passes both those Check Engine light tests--on with key, off while cranking--then your problem is something else.
  • Check for codes again. Whatever is causing this may have triggered a Continuous (memory) code
  • Unplug the MAP again, see what happens
  • Check for spark out the coil
  • Listen for your fuel pump being energized
  • Double check your grounds at battery, body, etc
  • Also have a look at your fusible link terminals and wires on the B+ side of your starter solenoid. They feed power to your engine controls, and a broken, loose or corroded terminal there can cause powerful grief
Your intermittent nature is inconvenient, both in your life and for your diagnosis. This makes it more gratifying when you nail it, and I'm totally confident you will.
 
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Tiha

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I would think PIP or ignition module as well. Sounds like the typical heat soak condition. They work after they cool down.
 
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jimbronco91

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Again, but brevitized:

Check Engine light is big clue.

When it is not starting, watch your Check Engine light.
  • If it comes on with the key on, your EEC Power Relay is working
  • If it comes on while cranking, the PCM is not receiving the PIP signal
Those are the two biggest (and easiest) diagnostic tells for an EEC IV cranking no-start.

Check Engine light is big clue when it's not starting, and if it passes both those Check Engine light tests--on with key, off while cranking--then your problem is something else.
  • Check for codes again. Whatever is causing this may have triggered a Continuous (memory) code
  • Unplug the MAP again, see what happens
  • Check for spark out the coil
  • Listen for your fuel pump being energized
  • Double check your grounds at battery, body, etc
  • Also have a look at your fusible link terminals and wires on the B+ side of your starter solenoid. They feed power to your engine controls, and a broken, loose or corroded terminal there can cause powerful grief
Your intermittent nature is inconvenient, both in your life and for your diagnosis. This makes it more gratifying when you nail it, and I'm totally confident you will.
Thanks as soon as the rain stops I will.run the tests. OK
 

Jimbo26

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Meanwhile the family waits in bewildered suspense......and then Grandpa says-
This should be interesting.
Tune in next week for when cousin Gordy says-
I think he fixed it again.
 

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L\Bronco

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Hey Jim
Motech has given you an awesome list of checks on the next no start, nothing to add there.
In the meantime it might be a good plan to check for codes.
You might get a leg up in the diagnosis…or not
Cheers
 

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