Mechanical Fuel pump, no fuel

[wilsbronco]

My 81 Bronco had a fuel injected '87 engine in it when I bought it a couple years ago. After working great for months, it had a lot of electrical issues crop up, combination of leaking windshield getting to the fuse block and idiot at the shop who put my new pipes on the back ... melted wires when he welded one of the supports on. Anyway, gave up on fixing it all myself and sent it to a shop that I will never use again. 8 months later, the guy was finally done, at over 3 times the original price estimate, and I got my Bronco back. He converted it to a carb system and swapped out the electrical fuel pump for a mechanical one. Now I had the basics of how the fuel injection system and pump worked before, but I'm not sure of how it's "suppose" to work now, especially since I am having trouble again.

I got the Bronco back in March. It started dying while driving a week later, but it was the fuel filter that was pretty dirty (it had been brand new with the whole swap out). Replaced that and only had occasional trouble when I was running low on gas. Long term, I think I need to drop and replace the tank as there seems to be a lot of junk in it. As of a couple days ago, however, it died as I was leaving the house and refuses to start ever since. I have a glass fuel filter and there's no fuel going thru it. If I wiggle the fuel lines underneath the bronco, the inside filter moves around responding to the change in air pressure, so no clogs between the tank and the engine. There had been a "hum" noise before, similar to the one an electric pump makes, there isn't one now, but I don't know if a mechanical pump is suppose to make noise anyway. When I crawled under, one of the lines had a clamp on it, crimping it pretty good. No idea why that was there, but I tried taking it off to see if that made any difference, and nada.

 

[BroncoJoe19]

My brother once had a Cadillac. The tank was so rusted he replaced the fuel filter once every week or two, until he put a new tank in. That sounds like your issue.

An '87 would have had two electric fuel pumps; a low pressure one in the tank, and a high pressure one on the driver's side frame rail. They would have made the electrical humming sound that you used to hear. Not so with a mechanical one that only pumps as the engine is rotating.

A mechanical pump sucks gas out of the tank, and to itself (mounted to the engine) and then pushes it through the filter to the carb. If you have a cracked rubber hose, it'll **** air instead of gas. The other pinched off fuel line is probably the old return line (from the fuel pressure regulator) that I do not believe is used with mechanical pumps.

 

[miesk5]

yo Wils!

btw, good stuff Joe!

Too bad those hack so-called "mechanics" got their hands on it!

Disconnect the mech pump's fuel line on tank side and see if you have any flow... ( I do tis on my John Deere... pull fuel cap off.. wrap clean cotton rag or whatever around neck, blow hard...!!!!)' see if you have any flow thru line. I use a paper coffee filter to inspect any gasoline I buy before pouring it into the tractor or vehicles...so you can place a filter on a container and see what comes out of da tank... could be micro particles that build up and clog the filter.

Ad Joe mentioned, that tank is prob full of crap...so drain it and have it re-coated internally or... ding-ding..more $ see this source which is our SPONSOR, Jeff's Bronco Graveyard! ;

http://broncograveyard.com/bronco/i-30214-33-gallon-steel-gas-tank.html Our Price: $100.00

also see http://broncograveyard.com/bronco/c-95-bronco-fuel-systems.html for the straps, lock ring, etc.

Also check the Vent Tube for the tank; if collapased, it could cause a problem..

Vent Tube Replacement w/Extended Info & pics in an 85 (converted to EFI); "...extended 6 more inches over factory..."

Source: by Tim O (RED WAGON, redwagon) at http://www.supermotors.net/registry/6130/68508

If flow is good, pull pump and inspect it.

Look at the lever that meets the camshaft eccentric--

new Airtex pump is about $20.00

And as Joe cited about the 2 FPs in 87; there also is this;

Single-Function Reservoir in 84-89; "...The PN for the filter is given, but you shouldn't actually have a filter in there. It should be an external inline filter further up the frame rail - you only buy the reservoir filter to get the O-ring, and only then if you have some reason to open the reservoir bowl. Unless you're having fuel delivery problems that you've isolated to the reservoir, you should never open it..." Miesk5 NOTE; Steve deleted his post

Source: by Steve83 (Steve, That dirty old truck) at Ford Bronco Zone Forums

Single-Function Reservoir in 84-89; "...were only used on the early EFIs; carbs & diesels used electrically-operated tank-select valves, and later EFIs use an in-tank fuel delivery module (FDM) that performs these functions. The single-function reservoir (SFR) is used on vehicles with ONE gas tank, like Broncos, vans, & low-trim pickups. The reservoir is always inside the L frame rail beneath the driver's floorpan about 10" behind the frame fuel pump. The 10mm bolt heads are easy to access on the outer face of the frame rail, but some vehicles have a large heat shield that must also be removed...There's not much to the SFR (which is what ALL Broncos of those years have): the '88 version just has the cup & 1 check valve

Single-Function Reservoir Overview; "...Dual fuel pump systems must have a fuel accumulator between them. The model from BC Broncos is a multi-tasking wonder. Fuel accumulators store fuel from the low-pressure pump for the high-pressure pump. Storing fuel is a great idea for rock crawlers, as the accumulator holds a reserve of fuel, just in case gravity temporarily affects the gas tank. Accumulators also equalize fuel flow between the pumps. If one pump is pushing 72GPH and the other is only flowing 50GPH, something has to give. Once the accumulator is full, excess fuel flows out to the return fuel line, and back to the tank. This keeps the low-pressure pump from stressing the high-pressure pump. Normal accumulators stop there, but not the model from BC Broncos. They built one starting with a fuel filter. You get the accumulator and the filter all in one $70 package..."

Source: by Ryan M (Fireguy50 at http://fordfuelinjection.com/Inject_your_horse3.pdf

 

[wilsbronco]

Thanks both of your for your suggestions! I'm about to go outside and follow what ya'll said to try. When it was fuel injected, it did have 2 pumps, one inline, one in the tank. The guy that switched it to carb definitely removed the inline and the old filter/reservoir (I usually had to buy 2 filters each time since I'd mess up the o-ring on my first try). Now the line goes straight from the tank to the engine compartment. There it has a glass filter thing, which is convenient that I can see inside to know if the filter is getting dirty. I'm just not use to the new setup yet and am still not quite sure about everything I'm looking at and what it's suppose to do.

As for the dirty tank, I figured as much and have already started looking for a replacement. I'm just hoping to get it going semi-reliably for now while I wait for a tank to come in and a free weekend to do that.

yo Wils!

btw, good stuff Joe!

Too bad those hack so-called "mechanics" got their hands on it!

Disconnect the mech pump's fuel line on tank side and see if you have any flow... ( I do tis on my John Deere... pull fuel cap off.. wrap clean cotton rag or whatever around neck, blow hard...!!!!)' see if you have any flow thru line. I use a paper coffee filter to inspect any gasoline I buy before pouring it into the tractor or vehicles...so you can place a filter on a container and see what comes out of da tank... could be micro particles that build up and clog the filter.

Ad Joe mentioned, that tank is prob full of crap...so drain it and have it re-coated internally or... ding-ding..more $ see this source which is our SPONSOR, Jeff's Bronco Graveyard! ;

http://broncograveyard.com/bronco/i-30214-33-gallon-steel-gas-tank.html Our Price: $100.00

also see http://broncograveyard.com/bronco/c-95-bronco-fuel-systems.html for the straps, lock ring, etc.

Also check the Vent Tube for the tank; if collapased, it could cause a problem..

Vent Tube Replacement w/Extended Info & pics in an 85 (converted to EFI); "...extended 6 more inches over factory..."

Source: by Tim O (RED WAGON, redwagon) at http://www.supermotors.net/registry/6130/68508

If flow is good, pull pump and inspect it.

Look at the lever that meets the camshaft eccentric--

new Airtex pump is about $20.00

And as Joe cited about the 2 FPs in 87; there also is this;

Single-Function Reservoir in 84-89; "...The PN for the filter is given, but you shouldn't actually have a filter in there. It should be an external inline filter further up the frame rail - you only buy the reservoir filter to get the O-ring, and only then if you have some reason to open the reservoir bowl. Unless you're having fuel delivery problems that you've isolated to the reservoir, you should never open it..." Miesk5 NOTE; Steve deleted his post

Source: by Steve83 (Steve, That dirty old truck) at Ford Bronco Zone Forums

Single-Function Reservoir in 84-89; "...were only used on the early EFIs; carbs & diesels used electrically-operated tank-select valves, and later EFIs use an in-tank fuel delivery module (FDM) that performs these functions. The single-function reservoir (SFR) is used on vehicles with ONE gas tank, like Broncos, vans, & low-trim pickups. The reservoir is always inside the L frame rail beneath the driver's floorpan about 10" behind the frame fuel pump. The 10mm bolt heads are easy to access on the outer face of the frame rail, but some vehicles have a large heat shield that must also be removed...There's not much to the SFR (which is what ALL Broncos of those years have): the '88 version just has the cup & 1 check valve

Single-Function Reservoir Overview; "...Dual fuel pump systems must have a fuel accumulator between them. The model from BC Broncos is a multi-tasking wonder. Fuel accumulators store fuel from the low-pressure pump for the high-pressure pump. Storing fuel is a great idea for rock crawlers, as the accumulator holds a reserve of fuel, just in case gravity temporarily affects the gas tank. Accumulators also equalize fuel flow between the pumps. If one pump is pushing 72GPH and the other is only flowing 50GPH, something has to give. Once the accumulator is full, excess fuel flows out to the return fuel line, and back to the tank. This keeps the low-pressure pump from stressing the high-pressure pump. Normal accumulators stop there, but not the model from BC Broncos. They built one starting with a fuel filter. You get the accumulator and the filter all in one $70 package..."

Source: by Ryan M (Fireguy50 at http://fordfuelinjection.com/Inject_your_horse3.pdf