Backfire at highway speed

[Rumbler tag]

As Tpremru says, it could be either, I would start at the pumps, (remember, you have 2, hi press on the rail, low press in the tank. Id start on the in tank pump.)
Get it to start acting up, and pull the fuel line that feeds the high press pump. measure the volume there. (It should be a quart in 30 sec)
Cheers

Ok thank you that is very helpful, when replacing the pumps what would you recommend for a good brand?

 

[Tpremru]

Ok

Ok I will make sure to check for proper voltage when replacing both pumps and the connector by the master cylinder, any recommendations on the brand I should get I’m thinking about a BOSH for the hp pump and a whole new drop in Delphi system for the lp pump

I have had 2 new rail pumps and i'm going to get the 3rd new one because of 2 years of running that pump dry so many times probably not good and it sounds funky sometimes. It currently has a Napa but i don't know which one they put in and replaced the Delphi. In a couple weeks i'm going to put in the Bosch that you get at Napa AKA "Part #: BSH 69100".

As for the in-tank - if you have the original still in tank consider "trying" to rebuild it - new float, new pump(Napa Part #: BSH 69115) and a new rheostat. The pump is no brainer get at napa, the float may not be too hard to find but some guess work on the rheostat could be a econline, mustang and a continental that i have seen before looks the same. Or maybe yours is in great shape. You won't save money by rebuilding it so only do it if you are picky (like me) or only need a pump. The other part about this is the rheostat for Ford up to 1986 - 73-10 Ohms but when you buy an aftermarket they almost never tell you those specs. Since i have had 5 different brands in mine i saw an inaccurate gas guage of different sorts. Sometimes inaccuracy can be helped during installation if there are 2 people doing that where you have to bend the float up or down before you install if you catch my drift. If you are not picky just throw in an aftermarket and sometimes when you have 5 gals you read E and you have a full tank reads past F. I actually bought a NOS for 130 my guage is good now!

 

[Rumbler tag]

I have had 2 new rail pumps and i'm going to get the 3rd new one because of 2 years of running that pump dry so many times probably not good and it sounds funky sometimes. It currently has a Napa but i don't know which one they put in and replaced the Delphi. In a couple weeks i'm going to put in the Bosch that you get at Napa AKA "Part #: BSH 69100".

As for the in-tank - if you have the original still in tank consider "trying" to rebuild it - new float, new pump(Napa Part #: BSH 69115) and a new rheostat. The pump is no brainer get at napa, the float may not be too hard to find but some guess work on the rheostat could be a econline, mustang and a continental that i have seen before looks the same. Or maybe yours is in great shape. You won't save money by rebuilding it so only do it if you are picky (like me) or only need a pump. The other part about this is the rheostat for Ford up to 1986 - 73-10 Ohms but when you buy an aftermarket they almost never tell you those specs. Since i have had 5 different brands in mine i saw an inaccurate gas guage of different sorts. Sometimes inaccuracy can be helped during installation if there are 2 people doing that where you have to bend the float up or down before you install if you catch my drift. If you are not picky just throw in an aftermarket and sometimes when you have 5 gals you read E and you have a full tank reads past F. I actually bought a NOS for 130 my guage is good now!

On rock auto the whole assembly made by Delphi seems pretty good it has the specific ohms for the fuel gauge so I’ll probably go with that

 

[Motech]

Ok so I finally got around to putting a fuel gauge in place I have videos of what the gauge does I don’t know how i would share them though, so starting and idling it stays around 30 psi once I put it in drive it stays around 28 and will remain there while costing and not touching the gas but when I was at highway speed and gave it gas the gauge would shoot all over the place from 20 to 40 psi and then when I really put the pedal down it would shoot anywhere from 0 to 40 the gauge was almost a blur because of how fast it was changing pressure. Should I go ahead and address the whole fuel system now?

Make darned sure your connections are impeccable. That alone could cause your symptoms, especially if, as you say, "...at highway speed and gave it gas the gauge would shoot all over the place from 20 to 40 psi and then when I really put the pedal down it would shoot anywhere from 0 to 40 the gauge was almost a blur because of how fast it was changing pressure"

That almost cries out voltage drops.



On your pump choices...

Ok

Ok I will make sure to check for proper voltage when replacing both pumps and the connector by the master cylinder, any recommendations on the brand I should get I’m thinking about a BOSH for the hp pump and a whole new drop in Delphi system for the lp pump

Bosch is excellent for frame-mount pump. They are the OE manufacturer.

I've had issues with Delphi units, but typically entire replacement modules with sender and carrier. You might be better off--and LOTS cheaper too--if you install an in-tank pump motor only into your existing pump carrier assembly.

This is a Bosch unit in-tank pump motor kit. It's a direct fit, part no 69115, but might be tough to find.
Note it includes the pump strainer that most others do not.



My second choice for in-tank pump motor would be Denso, but I can't find one from my normal sources.



Here is a Delphi unit, which should perform OK. Being my third choice though, I'd look harder for that Bosch unit up there.
Note it does not include the strainer. See below.






This is the Delphi strainer unit, part no FS0120






And do your Fuel Pump Relay too. OE is no longer available, but this Standard brand no RY70 will work well.




And lastly, replace your filter too. I'd go with Motorcraft FG1060 as they are factory replacements, and much less costly than Wix, for example.
And though not shown, it will come with line clips.




Happy tracing!

 

[Rumbler tag]

Make darned sure your connections are impeccable. That alone could cause your symptoms, especially if, as you say, "...at highway speed and gave it gas the gauge would shoot all over the place from 20 to 40 psi and then when I really put the pedal down it would shoot anywhere from 0 to 40 the gauge was almost a blur because of how fast it was changing pressure"

That almost cries out voltage drops.



On your pump choices...



Bosch is excellent for frame-mount pump. They are the OE manufacturer.

I've had issues with Delphi units, but typically entire replacement modules with sender and carrier. You might be better off--and LOTS cheaper too--if you install an in-tank pump motor only into your existing pump carrier assembly.

This is a Bosch unit in-tank pump motor kit. It's a direct fit, part no 69115, but might be tough to find.
Note it includes the pump strainer that most others do not.

View attachment 31003

My second choice for in-tank pump motor would be Denso, but I can't find one from my normal sources.



Here is a Delphi unit, which should perform OK. Being my third choice though, I'd look harder for that Bosch unit up there.
Note it does not include the strainer. See below.


View attachment 31004



This is the Delphi strainer unit, part no FS0120

View attachment 31005




And do your Fuel Pump Relay too. OE is no longer available, but this Standard brand no RY70 will work well.

View attachment 31006


And lastly, replace your filter too. I'd go with Motorcraft FG1060 as they are factory replacements, and much less costly than Wix, for example.
And though not shown, it will come with line clips.

View attachment 31007


Happy tracing!

I can’t seem to find the Bosh in tank pump anywhere

 

[Tpremru]

Yeah the closet Napa here says "call store for availability" Bosch 69115. You might want to get the Delphi - or - Carter (long time aftermarket fuel products made in the USA) That was gonna be my next if i need one again not that i have experience with them but made in USA i like.
Carter on Amazon

 

[Motech]

I can’t seem to find the Bosh in tank pump anywhere

Me neither. Compromise is inevitable.

 

[Rumbler tag]

Yeah the closet Napa here says "call store for availability" Bosch 69115. You might want to get the Delphi - or - Carter (long time aftermarket fuel products made in the USA) That was gonna be my next if i need one again not that i have experience with them but made in USA i like.
Carter on Amazon

Replaced both pumps, the in line filter and bypassed the inertia switch and added a new fuel relay. No change whatsoever besides it starts a lot faster now, what could it be now? this thing is a money pit. All I can think of is a new ecm because that’s the only thing that’s not new. Also when it dies on the road after bucking I can literally put it in park and start it right back up

 

[Tpremru]

Sorry to hear that Rumbler tag. Mine was a money pit for over 2 years. But as Motech said:
"Make darned sure your connections are impeccable. That alone could cause your symptoms, especially if, as you say, "...at highway speed and gave it gas the gauge would shoot all over the place from 20 to 40 psi and then when I really put the pedal down it would shoot anywhere from 0 to 40 the gauge was almost a blur because of how fast it was changing pressure"

I don't know much but i learned a lot...and i wanted to put my 86 in "debug" mode so i could test each pump individually so what i did was:

1. cut off fuel pump plug that is under apron under master cyclinder (1 wire in and 2 wires out)
2. connect 1 wire in to one of the 1 wire out (use a wire nut)
3. shorted pin #6 of obd1 connector to ground (you can now tell which pump is running LOpump or HIpump when you turn key to ON)
4. use a stick and or a hand and wiggle wire on that specific pump from begin of pump to where it is connected under master cyclinder
5. if pump stays on and you don't get any obvious signs of shorting out then repeat the process by switching wire to other pump.

That's how i found out that i had a new plug on the low pressure pump in the tank that was never completly installed correctly. 1 wire was not pushed in all the way and it was a bad "electrical" connection that when heated up would cause issue similar to yours.

 

[Rumbler tag]

Me neither. Compromise is inevitable.

Replaced both pumps, the in line filter and bypassed the inertia switch and added a new fuel relay. No change whatsoever besides it starts a lot faster now, what could it be now? this thing is a money pit. All I can think of is a new ecm or distributor because that’s the only things that’s are not new. Also when it dies on the road after bucking I can literally put it in park and start it right back up

 

[Rumbler tag]

As Tpremru says, it could be either, I would start at the pumps, (remember, you have 2, hi press on the rail, low press in the tank. Id start on the in tank pump.)
Get it to start acting up, and pull the fuel line that feeds the high press pump. measure the volume there. (It should be a quart in 30 sec)
Cheers

Replaced both pumps, the in line filter and bypassed the inertia switch and added a new fuel relay. No change whatsoever besides it starts a lot faster now, what could it be now? this thing is a money pit. All I can think of is a new ecm or distributor because that’s the only thing that are not new. Also when it dies on the road after bucking I can literally put it in park and start it right back up

 

[Tpremru]

Well it's easy to replace the ECM yourself and if you replace the distributor yourself then maybe your between 250-300 more into the money pit. If it works great! If it does not fix it then you are back to where you were but sounds like "everything" in the chain has been replaced leading back to Motech saying "connections" - If you like your B2 you just don't give up...and it will be great when it's solved and all those parts are new! That's what kept me going!

 

[Tiha]

That is a tough one when it starts right back up.

Can you leave a fuel pressure guage on it? tape it to the outside of the windshield so you can watch it as the truck dies?

I am still not so sure that is the problem. I suppose could be ECM, Could even be some other electronic part getting hot. Just have to eliminate one at a time.

This stuff will drive you nuts for sure. Seems like you will never fix it, until you do.

 

[L\Bronco]

Replaced both pumps, the in line filter and bypassed the inertia switch and added a new fuel relay. No change whatsoever besides it starts a lot faster now, what could it be now? this thing is a money pit. All I can think of is a new ecm or distributor because that’s the only thing that are not new. Also when it dies on the road after bucking I can literally put it in park and start it right back up

Hey Rumbler:
Its going to be tough to diagnose as it only does it when driving. Tiha is right, redo the fuel press check with the guage taped to the shield and see if the pressure still bounces around while its hesitating.
As Motech said, it could be an intermittent bad connection.
At least then you will know if you are chasing fuel or something else.
Good luck
Cheers

 

[Motech]

Replaced both pumps, the in line filter and bypassed the inertia switch and added a new fuel relay. No change whatsoever besides it starts a lot faster now, what could it be now? this thing is a money pit. All I can think of is a new ecm or distributor because that’s the only thing that are not new. Also when it dies on the road after bucking I can literally put it in park and start it right back up

Don't know if it's been addressed, but was your body ground off the battery mentioned and looked at? If you've got green fuzzies on that ground connection that goes right over to the body, that will cause all kinds of crazy things.

 

[Old&Cranky]

May be a simple exercise in just replacing the throttle body or taking it off and giving it a good cleaning. Hard to find a new one. I found new, old stock in Detroit but was last one they had. Still have the old one.