4cyl 5.8
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Cross-Country
Joined: Mar 2016
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4cyl 5.8
New member, long time bronco owner.
Just picked up an '88 5.8 C6 not running. New plugs, wires, cap, rotor, fuel filter & fuel that didn't smell like it was the original 1988 fuel. Busts right off soon as the starter is engaged. But it's only hitn on 7,2,6&5. Dead miss on 4,8,1&3. Yep, kind weird how it's missing on 4cyl in consecutive firing order. But I can pull all 4 wires off the cap at the same time & it runs the same. Anyone else ever experience this?
I'm running13726548 counter clockwise & it runs like crap & shakes the Bronco but it does run. I tried the 5.0 f order just to see & it wouldn't start. I'm thinking maybe the ignition module or ECM but not really sure what could cause it to miss on 4cyl in a row. Pulled this thing out of a field where it has set for years. Could also be stuck injectors I reckon & right now that's the next direction I'm headed. Pulling the plenum & fuel rail to see if they are all firing.
2nd issue;
HP fuel pump runs continuis with key on. Isn't it supposed to shut off after 8-10sec?
Also it sat for 3days before I changed the fuel filter & fuel. But when I pulled the line at the filter it was still under pressure.
Just picked up an '88 5.8 C6 not running. New plugs, wires, cap, rotor, fuel filter & fuel that didn't smell like it was the original 1988 fuel. Busts right off soon as the starter is engaged. But it's only hitn on 7,2,6&5. Dead miss on 4,8,1&3. Yep, kind weird how it's missing on 4cyl in consecutive firing order. But I can pull all 4 wires off the cap at the same time & it runs the same. Anyone else ever experience this?
I'm running13726548 counter clockwise & it runs like crap & shakes the Bronco but it does run. I tried the 5.0 f order just to see & it wouldn't start. I'm thinking maybe the ignition module or ECM but not really sure what could cause it to miss on 4cyl in a row. Pulled this thing out of a field where it has set for years. Could also be stuck injectors I reckon & right now that's the next direction I'm headed. Pulling the plenum & fuel rail to see if they are all firing.
2nd issue;
HP fuel pump runs continuis with key on. Isn't it supposed to shut off after 8-10sec?
Also it sat for 3days before I changed the fuel filter & fuel. But when I pulled the line at the filter it was still under pressure.
Fleet Mechanic
Joined: Dec 2006
Posts: 1,925
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From: Phoenix, AZ
Well a quick test before pulling injectors would be to see if the 4,8,1 and 3 wires are getting spark. I know you said the engine didn't make a difference when unplugged, but it's good to know for sure.
I usually just take a large screwdriver and shove it in the end of the wire that goes on the spark plug, then ground it out against a grounded piece of metal on the truck. If you get a spark, then you know you at least have juice to the wires! Be a little careful when you do this by the way! They probably make a special tool you can shove in the wire instead to test for spark, but this way is free and easy, just a little more dangerous.
If you don't get spark, then you know you have to address that first!
I'm not familiar with a dual pump setup on these trucks. I know on my 96, the fuel pump runs continuously though. I can hear it whining constantly, especially when it's colder out.
I usually just take a large screwdriver and shove it in the end of the wire that goes on the spark plug, then ground it out against a grounded piece of metal on the truck. If you get a spark, then you know you at least have juice to the wires! Be a little careful when you do this by the way! They probably make a special tool you can shove in the wire instead to test for spark, but this way is free and easy, just a little more dangerous.
If you don't get spark, then you know you have to address that first!
I'm not familiar with a dual pump setup on these trucks. I know on my 96, the fuel pump runs continuously though. I can hear it whining constantly, especially when it's colder out.
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
That and the fact the EFI system in this truck fires the injectors in batches of 4 leads to the most likely source of your problem.. rodents chewing on wires.
Fleet Owner
Joined: Oct 2005
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From: Kentucky
I would agree with Paul but the injector firing does not match the cylinders you say are active.
Cylinders 1,4,5,8 share a common and Cylinders 2,3,6,7 are fired on the other
Perhaps it is rodent related but not the typical eating through one wire, it has to be multiple.
Cylinders 1,4,5,8 share a common and Cylinders 2,3,6,7 are fired on the other
Perhaps it is rodent related but not the typical eating through one wire, it has to be multiple.
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Cross-Country
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rla,
Thanks for the schematic, it's about to come in handy. All visible wires look to be good however the only nest I found was under the plenum.
Thanks for the help guys,
I'll let ya know what I find.
Thanks for the schematic, it's about to come in handy. All visible wires look to be good however the only nest I found was under the plenum.
Thanks for the help guys,
I'll let ya know what I find.
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Cross-Country
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Looks like I'm gonna need an injection harness. Wires on 3&4 are gone, the rest look good. Ran a compression check & cyl8 is low (90lbs on 3rd bump) the rest were all above 130 on 3rd bump. Still no explanation for cyl 1 or 8 being a dead miss. When I pulled the plugs, the porcelain on cyl 1&8 were still white the rest were black. They've had maybe 30min run time.
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Cross-Country
Joined: Mar 2016
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Honestly I'm hoping it's just a stuck ring that will free up after I get it back up & running. It has been known to happen & that's the cheapest way out, lol. I am gonna pull the covers & measure lift at the rockers, lobes do wear down on occasions. Being it's a roller motor it shouldn't be an issue.
Senior User
Joined: Jan 2014
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From: Indiana
That should be a flat tappet in 88 I would think,You could try putting some trans fluid in the low cylinder to see if it will works things free.I would take the oil cap off and crank it over and listen to see if your getting blow-by.
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Howdy Chrismd,
Thanks for the reminder on the ATF, that's one I haven't used in years & had forgot about.
It does have a little blow-by. But at the moment that's not an issue. It'll be pulled & rebuilt later on anyway. Right now the goal is to get her up & running to figure out what all is gonna have to be done.
Only 13,xxx on the mile o meter. Now I'm sure there is a one in front of that but the interior is in too good of shape for it to be 213,xxx.
Thanks for the reminder on the ATF, that's one I haven't used in years & had forgot about.
It does have a little blow-by. But at the moment that's not an issue. It'll be pulled & rebuilt later on anyway. Right now the goal is to get her up & running to figure out what all is gonna have to be done.
Only 13,xxx on the mile o meter. Now I'm sure there is a one in front of that but the interior is in too good of shape for it to be 213,xxx.
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Howdy Guys,
Finally have time to get back to the Bronco. Replaced the rat chewed injector harness with a junkyard harness that looked to be in good shape. It ran better but still really ruff. Pulled out the noid lights & no pulse on cyl's 1,4 & 5.
Finally have time to get back to the Bronco. Replaced the rat chewed injector harness with a junkyard harness that looked to be in good shape. It ran better but still really ruff. Pulled out the noid lights & no pulse on cyl's 1,4 & 5.