Stumbles very intermitantly - Fuel pressure??

[Jesus_man]

After I got my inertia switch mounted properly I haven't had any issues with it running good. Last night I was taking it into town. It started easily as usual and I started backing out of the garage. 10 seconds later it sputters and dies. Will not restart. I check the valve on the fuel rail and fuel barely dribbles out even after cycling the key several times. I end up having to take another vehicle.

This morning I run out there, have my son turn the key on and I fill the HP fuel line pressure. I hit the valve on the fuel line and LOTS more fuel comes out. So I have my son start it and it does easily and continues to run. I have him shut it off and try again and it starts again... So now it appears it fixed itself?

I have two brand new fuel pumps, the LP carter, and HP Airtex E2000, complete with new fuel filter.

This rig used to be very reliable and I know there are going to be some teething issues before I can trust it again, but that doesn't make it any less frustrating?

Any ideas on where I should look?

[Viperwolf1]

Replace the fuel pump relay.

[Jesus_man]

I have one used spare but this one is brand new with Efiguy's engine harness.

Still worth a shot.

Edit to add that I could hear both pumps the whole time. If the relay was acting up wouldn't the fuel pumps not work?

[ZOSO]

I have one used spare but this one is brand new with Efiguy's engine harness.

Still worth a shot.

Edit to add that I could hear both pumps the whole time. If the relay was acting up wouldn't the fuel pumps not work?

Regulator might be sticking open. I had that happen on mine when I first tried to start it.

[Jesus_man]

Did you replace it or??

That makes some sense tho. When the trouble started that night I could hear both pumps pumping, but they would stop after a couple seconds (always assumed they stopped at a certain pressure). To me that means the relay is ok.

It would barely sputter that night, as in almost want to start but not too convincingly. Felt starved for fuel.

It would also explain why it fixed itself too.

It could also contribute to my other issues where I suspected the inertia switch...

[Jesus_man]

I'm back to having issues again. The past 40 miles or so were bliss, but I hadn't changed anything. Today my dad and I run into town about 7 miles and it sputters and dies. Very hot today here. I pull the vacuum line off the pressure regulator hoping to hear something inside change. Nothing (at least that I could hear, but there was a fair amount of ambient noise. I check the valve on the fuel rail and I have pressure as fuel sprays out. We check that the spark is good. So I jump back in and it fires up again and didn't have any trouble running to the parts store and the fuel station and all the way back home. There is potential it was low on fuel I suppose, but I really have no way of knowing. I put in 10 gal today, which at a minimum is 100 miles for me.

I have not changed out any parts yet. Fuel pressure regulator was on my short list, but now I still have pressure in the rail after the failure.

TFI module was cool to the touch. Coil was warm, but not unusually so.

[Rox Crusher]

You need to know how much fuel pressure you have at the rail and how quickly it bleeds off when engine is turned off

Is there a s schreader valve on the rail ?

[Jesus_man]

Is there a s schreader valve on the rail ?

There is. Time for a gauge setup I guess??

[ZOSO]

Is there a s schreader valve on the rail ?

There is. Time for a gauge setup I guess??

Yup. get the adaptor and gauge on there.

[Jesus_man]

So once the Schrader valve is removed the threads are 1/16" female NPT threads. So I need a 1/16" MNPT to 1/8" FNPT.

This would work right?
https://www.mcmaster.com/#9171k231/=18hf5iu

Then this:
https://www.summitracing.com/parts/sum-800199/overview/

[Eck]

So once the Schrader valve is removed the threads are 1/16" female NPT threads. So I need a 1/16" MNPT to 1/8" FNPT.

This would work right?
https://www.mcmaster.com/#9171k231/=18hf5iu

Then this:
https://www.summitracing.com/parts/sum-800199/overview/

Yup- that'll work.


Sent from my iPhone using Tapatalk

[Rox Crusher]

There are versions of the adapter that incorporate a 45 degree bend which makes it easier to read the gauge

[Jesus_man]

Last night I order the parts I need to install a gauge. And while I am preparing to load the bronco onto a trailer for a car show today, it dies. I fiddle with things for a while and decide if it will fire, I will b-line it for the garage so I can work on it in the lights of the garage. Albeit, the no wind, 90* 120% humidity garage! Anyway, I do get it to the garage, and realize in order to get the regulator off, I will have to loosen the fuel rail. I do that, and make a run to O'reilly's about 20 minutes before they close. I pick up a regulator for a '91 Mustang 302 as that seems to be the one that matches the mounting pattern as my original. It's a difference depth, but I decide to give it a try. Install it and bronco fires up. I use it to pull the trailer out of my backyard and leaving it running for a solid 15 minutes, get it loaded without issue. While we always hope we have something fixed, I'm not yet convinced it is. Only time will tell. I am just praying I can get it off and back on the trailer today at the carshow.

[Jesus_man]

I got my reducer and gauge installed today with fuel safe teflon tape:



Holds pressure in the mid-30's. If she dies again, I'll at least have a leg up on diagnosis!

[Jesus_man]

My bronco began to stumble again today. Had been driving around town for maybe 4 minutes and then it just tries to die. I coaxed it along for about 30 seconds and didn't have any more trouble for the rest of the 8 miles home. I was not in a good place to check fuel pressure but it was above 30 when I pulled into a parking lot after it began running good. The fuel gauge was bouncing between 30 and 35. Looked again at home and it was steady at 33. Would the bouncing intricate anything?

[EFI Guy]

Don't know how I missed this thread, give me a ring when you have a minute.

[Jesus_man]

Don't know how I missed this thread, give me a ring when you have a minute.

Will do! I assume evenings work best? I'm a no go for Monday, and I might sub for softball on Tuesday, but I'll call if not. During the day would work for me, but I don't want to interfere with your work!

[Jesus_man]

Don't know how I missed this thread, give me a ring when you have a minute.

So after our conversation, we came up with a gameplan.

#1 - check to see if both pumps are running off the same relay.
#2 - swap relays with the O2 circuit if I have another issue.
#3 - check fuel pressure whenever the stumble occurs.

It's been running great again for several trips to town and back...and am slated to hit the local trails here in a week...

But I did some looking around today.

on #1, I did find that both pumps are running off the same relay. So I'll need some guidance on how best to remedy that. I have power running near the HP pump for my OBA clutch switch. I could tap into that with a relay for the LP pump?? But I know there needs to be signal wires for the relay, so that is where I need help.

Thanks!

[Gunnibronco]

I'm curious about this. I'm running a Carter LP pump & E2000 HP pump off a single relay. Is the amp draw too much for 1 relay? Wish I knew about this while I was installing my new harness.

[Viperwolf1]

I'm curious about this. I'm running a Carter LP pump & E2000 HP pump off a single relay. Is the amp draw too much for 1 relay? Wish I knew about this while I was installing my new harness.

My '74 uses those same pumps on a single relay and it hasn't been a problem.

[Jesus_man]

OK, so that is comforting... Now I just have to wait for it to do it's thing and check fuel pressure. Maybe I should have routed the gauge in the cab??

[Gunnibronco]

I'm curious about this. I'm running a Carter LP pump & E2000 HP pump off a single relay. Is the amp draw too much for 1 relay? Wish I knew about this while I was installing my new harness.

My '74 uses those same pumps on a single relay and it hasn't been a problem.

Thanks, good to know.

[Jesus_man]

I went on my first mid-west trail ride yesterday and it didn't turn out as well as I had hoped. I have some material for the "suck" thread.

Anyway, about 3 miles into the trail, my bronco starts to stumble and die. I get it to run another 100 yards before it dies again. So I am checking fuel pressure and the gauge reads 0. I prime the system with the key and I get 35psi, but as soon as I try to start it, pressure bottoms out again. And my E2000 pump is nearly too hot to touch.

I have emailed Airtex and they have a lifetime warranty, so i am hoping to start there, if they'll honor it. Otherwise, I may disconnect the HP pump and prime the system again and see if the Carter is doing it's job. I also have my original fuel pump that I may swap back in and see where that puts me.

I swapped relays to no avail.

I got dragged out to my truck where I left it the rest of the day. Then I loaded it under it's own power after it had cooled off.

Am I missing anything here? I have to assume the hot fuel pump isn't normal operation.

[ZOSO]

Pump vapor lock. Mine did that on me once it all got hot. threw some ice on the pump for a few minutes. Would fire right back up. I cured it by going intank.

[Jesus_man]

Well, I guess that is good to hear you had a that issue. I was wondering if the heat would do that.

I'm not sure I want to go in-tank, but perhaps Airtex will warranty this pump and I'll try another. Then ask for a refund if it's not working.

For those who have the standard 23 gallon tank...what does the pickup look like? Are there any components on there that rot away causing it to suck air? I doubt this is my issue since I have trouble-free periods of time. But just wanted to check.

[Kinder]

Standard 23 gal BC or WH carb tank? If yes, there is a small rubber hose connecting to a steel tube inside the tank, at least on mine there is. But I'd say if that's loose you'd have problems all the time not just when hot.

[Jesus_man]

Standard 23 gal BC or WH carb tank? If yes, there is a small rubber hose connecting to a steel tube inside the tank, at least on mine there is. But I'd say if that's loose you'd have problems all the time not just when hot.

I *think* it's a BC, but I didn't install it and it's been there for years!

I also agree that with that hose rotted, I'd have trouble all the time!

I let it idle on high yesterday for nearly an hour and it ran perfect the whole time, although the HP pump was still very hot! It was hot even just after a few minutes of running. The fuel gauge does jump around a bit from like 28-30 psi while idling constantly.
I hope to hear from Airtex today and will report back.

[plumbdoctor]

Do you have rubber hose from tank to Carter pump?
I have the same set up, the only issue I had was a small crack in the rubber hose from tank to pump, it would suck air into the system and stumble

[Jesus_man]

Do you have rubber hose from tank to Carter pump?
I have the same set up, the only issue I had was a small crack in the rubber hose from tank to pump, it would suck air into the system and stumble

I do. I did inspect it, but if it's small enough NOT to leak then I could have missed it.

[TOOLMAN]

Standard 23 gal BC or WH carb tank? If yes, there is a small rubber hose connecting to a steel tube inside the tank, at least on mine there is. But I'd say if that's loose you'd have problems all the time not just when hot.

I *think* it's a BC, but I didn't install it and it's been there for years!

I think if it's a BC/WH tank, it will bolt to the frame via some metal wedges. If it's the NWMP tank, it has straps. Also the NWMP tank had a tag/sticker on the driver side top IIRC. Someone correct me if I'm wrong.