I can hear the turn signal in the fuel pump

[Johnnyb]

The fuel pump is wired from the battery fused through a relay and then to the pump.
The alternator is 4G with a standard fusible link to the battery.
I can turn on the headlights and every other accessory in the vehicle and watch the voltage hold steady above 14V.
When I turn on the turn signals however the voltage fluctuates about 2/10 of a volt when the signals flash and I can hear it in the fuel pump.
Would this be considered normal or is it a failure of the alternator to react quickly enough to the load caused by the turn signals?

THX,
JB

 

[tutone]

I wouldn't think that is a failure of the alternator, but maybe you have the flasher or wiring pulling down the voltage more than it should? .2 volts isn't a lot but seems excessive for that. If it happens on both left/right, I'd suspect the wiring to the flasher. Maybe do a voltage drop test? Maybe you have a weak ground wire somewhere.

 

[Oldtimer]

Is fuel pump in (near) tank?
I would suspect ground issues between tank/pump and frame, and rear turn signals and body/frame.
The only factory ground between frame and body on early models was the ground wire from tank sender to the body/frame.

 

[Johnnyb]

Since the turn signals are through the painless harness, and the fuel pump is basically wired from the battery I was not thinking ground issues but I'll check.
Other accessories come on and the voltage drops but recovers immediately, the turn signals are intermittent and I was wondering about that?

 

[Broncobowsher]

Headlights are a bigger load than turn signals.
The late model alternator recovery time is crazy fast, few milliseconds.
Do the hazards also cause the voltage dip? What about hazards and brakes together (that bypasses the flasher and keeps all the turn signals on continously, at least with the in dash hazard switch)

You may be seeing a 0.2V drop with the signals on, but does the alternator really drop that much? Do you get that drop between the sense wire (the one that should go to the battery but most people just loop to the alternator output) and the alternator case? If so, well the alterantor really isn't keeping up with the turn signals, which would be weird. It does? Start looking for the 0.2V drop. Is it on the ground side? alternator case to battery negative post. I keep going to the alternator case as the ground reference as that is where the voltage regulator sees ground at. So also alternator case to body, engine block, etc. And the positive side as well. Where is that 0.2V drop happening at? And it may not all be in one place. Might be a fraction here and a fraction there. But it will all add up. Time consuming with a lot of dead ends. But that is the game with electrical diagnostic work.

 

[Johnnyb]

@Broncobowsher , I will do some checking around and post back here.

 

[73azbronco]

welcome to analog age. Pretty normal if you ask me, but check ground for fuel pump. Old school bulbs? Yeah, normal.

 

[MarsChariot]

What 73azbronco said. I have another vehicle with an electric fuel pump. Before I went to all LED lights, the turn signal flasher would change the pitch on the fuel pump in time with the flasher. Fairly normal but nothing worrisome.

 

[ntsqd]

What fuel pump are you using that you can hear it? That's what I'd be changing.

 

[DirtDonk]

When the engine is not running, how did the turn signals and flashers work? Like normal?
What about the brake lights only?

Perhaps more importantly, how is your alternator wired?
You shouldn’t be seeing any unusual characteristics caused by the alternator itself. The battery is the dampener in the system and power should be coming from there.
Not only is the pump wire directly to the battery through a relay, but the alternator should be dumping it’s load directly into the battery as well.
Perhaps there is something in the connections there at the battery that isn’t playing nice with the way Painless wires things.

 

[Johnnyb]

What fuel pump are you using that you can hear it? That's what I'd be changing.

It's a wild horses frame mounted pump. The external pumps are pretty commonly noisy, you can't hear it driving down the road but while sitting at a stoplight with your turn signal on it is noticeable but not bothersome.

 

[Yeller]

The only way that I have found to have a quiet external fuel pump is to use a Ford mounting bracket. There are 2 sizes, those from 90’s F150 and E150, for larger diameter Bosch pumps and 99-02 diesel Super Duty for the smaller diameter Walbro style pumps. FYI the Walbro style pump fits in the F150 bracket with the foam sleeve installed most of the pumps come with. Took my pump from being so loud it could be heard running 70mph with no top, loud exhaust and MT tires to barely noticeable not running in my quiet garage.

@WILDHORSES this is an item someone needs to reproduce. The only current sources is a good friend like @toddz69 to dig them out of his honey holes in the desert, search eBay, or manage to find a Motorcraft replacement pump that comes with one. I currently am on the lookout for more, just installed my last one.

 

[ntsqd]

I rubber mounted this Walbro pump now about 12 years ago. Absolutely quiet, cannot hear it unless you're standing next to it when the engine is being started, and even then you have to know what to listen for. Can't hear it from inside the car at all. I occasionally hear from the current owner and it's still going strong. The inlet hose end was changed to a 45° after this pic was taken and that small kink is long gone. I wouldn't mount it this way on an off-road vehicle, but for a street car it worked well.

I copied the Ford foam mount method for the FJ60's EFI external pump. I used exhaust tubing, hose clamps, and some foam from McMaster. It, and the Wix 33481 fuel filter were attached to a rubber isolator mounted cradle.

 

[ba123]

Since the turn signals are through the painless harness, and the fuel pump is basically wired from the battery I was not thinking ground issues but I'll check.
Other accessories come on and the voltage drops but recovers immediately, the turn signals are intermittent and I was wondering about that?

Maybe your power source you used for the Painless harness? Did you wire that directly to the battery or did you go to some other contact point?

If not direct, and some other contact point, maybe try jumping it direct and test.

 

[toddz69]

I currently am on the lookout for more, just installed my last one.

I'll look for some more! Getting harder and harder to find those rigs in the yards.

Todd Z.

 

[ntsqd]

I have one from a Merkur XR4Ti, could look for them under those, too. LOL..........

 

[toddz69]

I have one from a Merkur XR4Ti, could look for them under those, too. LOL..........

Years ago, I pulled one on your recommendation! Not sure if it's still in the collection or not.....unfortunately the XR4ti's disappeared from the yards at least 20 years ago...

Todd Z.

 

[ntsqd]

I don't recall the exact details, but they aren't quite the same bracket as the one pictured above. I saw one in the local yonke about 8 years ago. Hadn't seen one in decades before that.

For the fuel pump to be "broadcasting" the turn signal on/off function the circuit voltage is dropping for some reason. I'm with broncobowsher in that the Alternator should not have any trouble picking up the system voltage. Unless it's not working very well. Leaves me with either something in the grounding that is the problem, or the alternator isn't working well. Does it do it at cruising speeds or even a high idle, or only at a normal idle?