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Discussion Starter #1
I need some troubleshooting help, so here my story. (Truck info under name, still).

While leaving the camp grounds, I switched to my rear tank to idle. I normally keep about 3 gallons in it for idling only since the seal on the tank isn't 100%. The truck started to die, so I switched back to the front tank. Then I made the mistake of trying to figure out why it started to die and switched back to the rear tank. Truck started to die again, so I hit the switch again. Truck died anyway. I completely lost power to the fuel pumps, andhardwired battery power to the tank selector switch to make it home, overfueling horribly (black exhaust, bogging and rough idle). Found out that one or more of the fusible links connected to the starter relay had melted through. I replaced the links with standard blade fuses and the large 10 ga. wire ring terminal with a crimp on one.

Now I have power to the pumps as I should, but the truck still just barely keeps from overfueling at idle and rolls coal constantly and continues to bog under quick throttle. Even after resetting the battery (and therefor the EEC IV), I still get codes21, 22, 53, 54, and 35 in that order. the codes state that the ECT, MAP, PFE/EVP Curcuit, TPS, and ACT sensors are all above voltage. Are there resitors in the fusible links as well or something? Alternator charges right where it should, about 14.4V (140 amp 3G conversion) and I've never had problems with the alternator or regulator since I put it on.

Any ideas? I'm almost at a loss on this one.
 

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aka: kemicalburns
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are you sure your FPR isnt shot and causing the over fueling????
 

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I need some troubleshooting help, so here my story. (Truck info under name, still).

While leaving the camp grounds, I switched to my rear tank to idle. I normally keep about 3 gallons in it for idling only since the seal on the tank isn't 100%. The truck started to die, so I switched back to the front tank. Then I made the mistake of trying to figure out why it started to die and switched back to the rear tank. Truck started to die again, so I hit the switch again. Truck died anyway. I completely lost power to the fuel pumps, andhardwired battery power to the tank selector switch to make it home, overfueling horribly (black exhaust, bogging and rough idle). Found out that one or more of the fusible links connected to the starter relay had melted through. I replaced the links with standard blade fuses and the large 10 ga. wire ring terminal with a crimp on one.

Now I have power to the pumps as I should, but the truck still just barely keeps from overfueling at idle and rolls coal constantly and continues to bog under quick throttle. Even after resetting the battery (and therefor the EEC IV), I still get codes21, 22, 53, 54, and 35 in that order. the codes state that the ECT, MAP, PFE/EVP Curcuit, TPS, and ACT sensors are all above voltage. Are there resitors in the fusible links as well or something? Alternator charges right where it should, about 14.4V (140 amp 3G conversion) and I've never had problems with the alternator or regulator since I put it on.

Any ideas? I'm almost at a loss on this one.
Sounds to me like a possible EEC problem. If all of those sensors are reading the same above voltage thing.
 

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What caused the meltdown? Did you find it? Fix it? A short to the fuel pumps? It may be that whatever shorted took the computer or still exist in the harness.

I'd check voltage too and from one of the sensors. If it's correct the computer is wrong. If it's high, well it's in the harness or computer.
 

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Discussion Starter #5
I believe that the short occured in the switch while switching back and forth from tanks so quickly while the engine was dying. I forgot to mention that I cutout the fuel pump relay and replaced it with the standard Bosch style and that I'm running without a knock sensor. The engine mounting bolts worked out and the engine dropped, causing the plate on the mount to shear the plastic off the discontinued knock sensor, but the plastic is still plugged into the harness.

I checked the voltage at the battery, new wiring where I replaced the fusible links, and power wires to both the fuel pump and EEC relay. All read within .2 volts of the battery charging at 14.4V. I know that the in tank pumps are still good and not the problem, but for some reason, something is sending those sensors out of range and causing the EEC IV to go into limp mode and severly overfuel. I did manage to keep her running long enough to do a KOER test (didn't get goosed to do a throttle test). The KOER test threw codes 98, 22, 54, 51 and 53 in that order. 98 just reads "hard fault present", 22 is the MAP sensor above test voltage again, and the 54, 51, and 53 aren't even suppose to show on a KOER according to FordFuelInjection.com's code list.

Going to replace the stock EEC relay with a Bosch style one this weekend as well for simplicity.
 

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Discussion Starter #6
I think that there is a short in the switch. It has been taken apart and checked with no issues visually. I flipped the selector switch today just to see if the rear tank pump was still ok as well and one of the blade fuses that I replaced the fusible links with have popped. I'm going to try tracing the power wires to the pumps and see what turns up, then replace the switch.
 

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I'm running without a knock sensor. The engine mounting bolts worked out and the engine dropped, causing the plate on the mount to shear the plastic off the discontinued knock sensor, but the plastic is still plugged into the harness.Going to replace the stock EEC relay with a Bosch style one this weekend as well for simplicity.
First off, from my experience, Bosch parts do not go well with Fords. Every Bosch part I have put on any one of my Fords has been rejected within weeks, if not days. 2nd, I wonder if an electronics shop could somehow rig up a rudimentary knock sensor for us?:scratchhe
 

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Discussion Starter #8
Found a knock sensor at the junkyard today while visiting my parents. Since they are a discontintued part, I will grab every one I can find next time I go and keep them on hand for other board members that need a replacement.

@Dave - The relay mod is just a "Bosch-style", as in standard black box relay as opposed to the stock $30 bastards that came stock in '87-'91 trucks.
 

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1) After you fix your short, replace the blade fuse with a fusible link of the correct size.

2) You likely have a problem with your EEC processor or connector. Disconnect your computer harness at the plug and check the condition of the pins. Look for corrosion and or water. Both are very common in the rust belt.

3) I usually prefer ford relays to the bosch style hecho in china parts. If you are willing to go to the bone yard to get a knock sensor, grab a few relays while you are at it.
 

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Found a knock sensor at the junkyard today while visiting my parents. Since they are a discontintued part, I will grab every one I can find next time I go and keep them on hand for other board members that need a replacement.

@Dave - The relay mod is just a "Bosch-style", as in standard black box relay as opposed to the stock $30 bastards that came stock in '87-'91 trucks.
I was just curious if some electronics shop could "rebuild" a knock sensor.
 

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I wonder if cardone would rebuild the knock sensor. It says here they have a rebuild, and return department to send requests to if your part isn't there.


http://www.cardone.com
 

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Discussion Starter #12
1) After you fix your short, replace the blade fuse with a fusible link of the correct size.

2) You likely have a problem with your EEC processor or connector. Disconnect your computer harness at the plug and check the condition of the pins. Look for corrosion and or water. Both are very common in the rust belt.

3) I usually prefer ford relays to the bosch style hecho in china parts. If you are willing to go to the bone yard to get a knock sensor, grab a few relays while you are at it.
The short is fixed, but the only place I know where I can get the fusible links, which are nothing but a few smaller wires, is from a junkyard. I already made may visit earlier in the week (no pull it yourself junkyards in my current area, only get to go when I visit my parents 80+ miles away).

After I get the ground wire near the knock sensor reattached (previous unrelated occurance, not attached at the time if this problem), I'm going to try resetting the EEC again and let it learn with the knock sensor in the curcuit. I'm hoping that this is the current problem since it was reset without the knock sensor before and the computer is trying to comensate by running in "limp mode" and overfuelling/throwing those other sensors above range. If the reset with the knock sensor fails to be the problem, then I will pull the EEC IV and look inside. The problem shouldn't be in the bulk connector since it was fine until this occurance with the grounding short in the fuel pump power. I'm really afraid that in this situation, somehow a resistor inside the EEC IV burnt out...If that's the case, I think this 300 will see it's last days in the truck with a HD 300 carbby intake and exhaust mani on it if I can't get ahold of a new manual tranny 4.9L EEC IV, or at least until I can get a boosted 6.9 oil burner in. The eventual plan is to run a 6BT and a tank heater in the rear tank for filtered WVO.

EDIT: Found an alternative descrpition for the CEL code 98 during the KOER test.

Code 98 (R) Electronic control assembly failure

Code 98 (O) Electronic Pressure Control (EPC) Driver open in EEC processor

Code 98 (R) Hard fault is present - FMEM mode


The FMEM refers to "Failure Management Effects Mode", aka, Limp Mode. Looks like the problem may lie with a dead EEC IV. I've searched other sites and found some things referring to it where the EFI controller was replaced and solved the problem...total suck...
 

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I picked and pulled a 95 MAF computer for only $35.

I need it but if you can pull one yourself, not expensive.
 

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Discussion Starter #15
The EFI computer is in fact dead. The problem with pulling on is that I don't have anyplace that I can get to easily that has an 8th generation F150 with a 300. All the 300's are in 9th gen trucks ('92-'96) and all the 8th gen trucks are diesel 7.3's.

So I will have some cash at my disposal soon for automotive purposes and I'll be doing one of 2 things. Either a carb'd 300 with an Offy 4bbl intake and a HD 300 exhaust mani (found one in the junkyard on an older F350, pretty rare) with forged internals and a mild cam and mild head P&P job. Or a 6.9L with the ZF5 behind it and a spool. I would rather go the diesel route, that way everything is already setup to drop in a Cummins in the future.
 

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The EFI computer is in fact dead. The problem with pulling on is that I don't have anyplace that I can get to easily that has an 8th generation F150 with a 300. All the 300's are in 9th gen trucks ('92-'96) and all the 8th gen trucks are diesel 7.3's.
I'm headed to the junk yard tomorrow... which computer are you looking for, 87-91 inline 6 300?
 

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Its a shame that your truck isnt a 92-96 because I was just at the yard this -weekend and pulled 25-30 ecm's out of every 92-96 truck I could find and a boatload of them were 300's...I'd say 85%
 

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Discussion Starter #18
@snook, I found the same, total suckage.

@Demonio, I would need one for an '87-'91 (preferrably '90-'91) with the 300 and a manual tranny.
 

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@snook, I found the same, total suckage.

@Demonio, I would need one for an '87-'91 (preferrably '90-'91) with the 300 and a manual tranny.
My dad replaced his about two months ago. 90 F150 with 300 six and 5 speed. He got his replacement computer from O'Reilly's Auto Parts. Autozone had them too, but were slightly more expensive and he personally likes O'Reilly's better anyway. Seems like it was about $130.00.

I am also not sure why a 92-95 computer will not work?

tim
 

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Discussion Starter #20
If I'm going to spend more than $100, it'll be on parts for either the turbo diesel or turbo 300 build (I like O'Reilly's better as well).

The '87-'91 EEC's have a 60 pin connector and control a speed-density system, '92-'96 have a 62 pin connector and are used on the MAF system.
 
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