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Open Roads Forum  >  Tech Issues

 > How to tell if fuel pumps are running by current draw?

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maillemaker

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Posted: 10/10/19 11:50am Link  |  Quote  |  Print  |  Notify Moderator

I would like to have an indicator lamp in the cabin that indicates if the fuel pumps are running or not.

One way to do this would be to plumb in pressure senders before and after the high pressure pump, but this would be difficult and expensive.

The fuel pump relays are easily accessible under the hood near the engine battery.

Is there a way I could monitor the current draw to power an indicator light to indicate that the pumps were running (and not just getting power)?

Steve


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JaxDad

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Posted: 10/10/19 01:33pm Link  |  Quote  |  Print  |  Notify Moderator

Mine has one...... It's called a CEL.

It lights up when the engine dies after it runs out of fuel with no fuel pump running.

Maybe I'm missing something? What would a light telling you the pump is on or off accomplish?

maillemaker

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Posted: 10/10/19 01:36pm Link  |  Quote  |  Print  |  Notify Moderator

Quote:

What would a light telling you the pump is on or off accomplish?


It would tell me whether my loss of fuel pressure is due to vapor lock or pump failure.

My CEL does not come on until the engine dies.

Steve

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Posted: 10/10/19 02:45pm Link  |  Quote  |  Print  |  Notify Moderator

You could install a Hobbs switch to a small led light, but not cheap $80 bucks my last one. Imo probably liquid fuel in till over engine, then liquid into vapor because of engine heat. So your pump might be working good, but fuel vaporizes before getting to where the fuel needs to be liquid at ie injected into cylindar.
Just you or is this common problem with your make and model.

time2roll

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Posted: 10/10/19 03:13pm Link  |  Quote  |  Print  |  Notify Moderator

maillemaker wrote:

Quote:

What would a light telling you the pump is on or off accomplish?


It would tell me whether my loss of fuel pressure is due to vapor lock or pump failure.

My CEL does not come on until the engine dies.

Steve
Most any indicator will do the same. Basically not a warning so much as an indicator of why the engine stopped.

How long do you expect the engine to run without a fuel pump? You may need some type of accumulator to store pressurized fuel. Or need to run dual fuel pumps and have an indicator when one stops or for the backup to start if pressure drops with an indicator backup has started.

Otherwise by current draw you would need an ammeter. Fairly inexpensive on ebay.


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mich800

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Posted: 10/10/19 04:36pm Link  |  Quote  |  Print  |  Notify Moderator

If they are having that many issues with vapor locking they are attempting to rig up a gauge just to determine if the fuel pump is operational, I would just tackle the symptom of heat in the engine bay. That is assuming they already troubleshot the issue and determined it is a vapor lock and not a fuel delivery problem. Just because the pump is running does not mean it is delivering adequate fuel pressure under load.

maillemaker

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Posted: 10/10/19 07:59pm Link  |  Quote  |  Print  |  Notify Moderator

You can see the whole issue here:

https://www.ford-trucks.com/forums/1089626-vapor-lock-in-an-efi-engine-2.html#post18890425

Quote:

You could install a Hobbs switch to a small led light, but not cheap $80 bucks my last one. Imo probably liquid fuel in till over engine, then liquid into vapor because of engine heat. So your pump might be working good, but fuel vaporizes before getting to where the fuel needs to be liquid at ie injected into cylindar.
Just you or is this common problem with your make and model.


Evidently this is a common problem with Ford 460 engines. If you google "Ford 460 Vapor Lock" you will see tons of people with this issue - when driving at speed, in hot weather, especially with the AC on, the engine will stumble and die, and backfire through the intake. After the engine cools for some 20-40 minutes, it fires up and runs fine.

I have been fighting this issue for about a year. At first I replaced the ICM, and thought I had it licked as it went all winter long without issue. But that was just because the weather was cold. Problem came back in the summer. I have replaced:

Radiator
Catalytic Converter
Distributor (and thus PIP sensor)
Spark Plugs and Wires
Engine Temperature Sensor
Idle Air Valve
In-Tank fuel pump

RV died again last week 2 hours into an 11-hour trip. Up until that point I had assumed I had a heat-related component failure, but now I am not so sure. I believe I probably have fuel boiling in the fuel rail. In the above link, there is another link to a guy who describes the same problem:

Quote:

Yes. In fact, after I replaced the tank pump (low-pressure), we had the problem again, and a shop replaced the high pressure pump on the frame rail below the driver's door because they said it was running a little low. They subsequently tested all the pressures, and they were fine.

I kept a FP gauge attached to the Schrader valve on the fuel rail during one trip after that. It ran at the correct pressure (I think it was 50 psi, but that was a couple of months ago, so that may not be exact); however, as soon as I climbed a long hill in heat over 85 degrees F, the pressure dropped to zero and stayed that way through multiple attempts to restart. When I pressed the release valve on the gauge, I got nothing more than a few spurts and drips of fuel; I was halfway expecting to get a high-pressure burst of boiled fuel, but got nothing like that.

After about 45 minutes, though, I was able to start it just fine, the pressure went immediately back up to 50, and we were on our way again. That happened three or four times in one trip, and it was always the same: a drop to zero FP in a hot climb, a 45-minute wait, and a no-problem start with FP at specs until the next big climb. It has never happened except when very hot, and then only when climbing long hills. No engine overheat, though.


So this guy has the exact same issue that others and myself have reported, and he captured zero pressure on the fuel rail at the time it was happening. He had already replaced his in-tank and hi-pressure fuel pumps.

There is a video on YouTube of a guy who claims he fixed his problem by replacing the Fuel Pressure Regulator.

So, we can be pretty certain that the problem is heat-related, and we can be pretty certain that it involves zero fuel pressure.

The question is, is it due to vapor lock, or is it due to a fuel pump overheating and shutting down somehow.

This weekend I am going to install a new fuel filter, and a GlowShift digital pressure gauge to the schrader valve on the fuel rail, so I can monitor the fuel pressure at the rail. But, even if I can capture the problem again (temps seem to have broken for the fall, so I may not see this problem again until summer), zero fuel pressure does not necessarily mean fuel boiling.

My suspicion is that these engines were designed and manufactured prior to the common adoption of ethanol-based fuels. Ethanol blended fuels have a lower vapor pressure than regular gasoline. It may be that the design was marginal with pure gasoline, but with ethanol when the temps get high enough, combined with the AC dumping more heat into the engine bay, that it is sufficient to boil the fuel in the fuel rail.

Evidently when the fuel vaporizes in the fuel rail, the pressure regulator interprets this as low pressure in the rail and stops sending fuel back to the tank (this is how it regulates the pressure), and this in turn would stagnate the flow of fuel in the line and let it get even hotter.

But anyway, there is the possibility that the pump(s) are failing.

I would like to monitor the status of the pumps electrically, if there is a circuit that could be devised to do so and drive an activator light on the dash installed somewhere. Just detecting power to the pump is insufficient, as the pump could be receiving power but not running. So I'm looking for an electrical way to determine the status of the pump.

Obviously I can install pressure gauges or Hobbes switches, but I was hoping there was a way to directly monitor power to the pump and be able to infer if it is operating or not based on current draw. Note I do not want to use a Fluke meter or similar current meter - I want a permanent gauge-driving setup.

I am also considering installing vent louvers in the hood on either side of the hood. I considered putting louvers along the entire rear edge of the hood but the cabin air intake is in front of the windshield and I do not want to drive hot engine air directly into the cabin air intake. So, if I install the louvers they will be on the outboard rear edges of the hood.

I am also considering insulating the fuel rail in the engine compartment.

But, all of this is for nothing if the true problem is the fuel pumps themselves. Hence I would like to come up with an electrical way to monitor if they are running or not.

I'm probably just going to go ahead and replace the high pressure pump as well. The low-pressure in-tank pump burned up about 5 years ago, and I replaced it with an AirTex E2060S turbine pump. But when the OEM pump burned up it took out the inertial switch and the fuel pump relays - it is possible that it damaged the high pressure pump also. I did not even know this van had 2 fuel pumps until a couple of weeks ago.

So, there's the long and short of the story.

time2roll

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Posted: 10/10/19 09:07pm Link  |  Quote  |  Print  |  Notify Moderator

maillemaker wrote:

Note I do not want to use a Fluke meter or similar current meter - I want a permanent gauge-driving setup.


Digital panel meter under $10 with shunt on ebay. Need to custom mount.

DC-100V 10A 50A 100A Voltmeter Ammeter LED Dual Digital Volt Amp Meter

shepfly

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Posted: 10/10/19 11:03pm Link  |  Quote  |  Print  |  Notify Moderator

If you truly have vapor lock try insulating your fuel lines from the tank outlet to the engine. Your fuel lines run forward with the exhaust pipes inside the frame rails. This creates very high temps for boiling you fuel! I cured my VL problem buy doing this on an old Bluebird with a 534 Ford gasser years ago. You can buy the purpose built insulation from Summit Racing or Jegs. Or if you have a doghouse, open it up and have someone pour cold water on you fuel lines! Worked for us! But got dammed hot in bus! Good Luck, Dave
,

MrWizard

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Posted: 10/11/19 12:26am Link  |  Quote  |  Print  |  Notify Moderator

current in the motor will drop, ONLY if the hot pump has an open circuit

a hot pump 'Stall' with out open circuit, will Increase current drain
and the pump motor will get hotter

unless it has an in motor temp over load AKA 'clik switch'

the ampmeter is the right idea

but better yet is to insulate the fuel lines, especially that big 'tin can' fuel filter

i'm ordering some 'Hot starter' shield wrap to insulate my fuel filter and external fuel pump


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