Testing electric fuel pump

[Gregs672000]

Greetings all, need some direction in an area I'm not so good at... electrical. My wife and I were headed out for a drive today but I started getting weird lean air/fuel ratios on the meter and noted fuel pressure was down on the regulator. It had been doing this for a short time on start up then clearing up in the past few weeks. Drove the car home, and it acted up intermittently doing the same thing (lean), which usually means fuel pump (remember, I'm fuel injected). Checked voltage at the pump and it had only 9-10 volts when connected and running but the wires themselves had 12+ when NOT connected to the pump. I hooked up my emergency back-up pump and it had 11.6volts when energized (the system does a short priming pulse when first energized, then waits for the car to crank before engaging power again, so I could operate it outside the tank for short tests). When testing the Bosch it showed 9 volts or so on the priming pulse, improved some with the engine running and the alternator energized but never more than 10+. I'm thinking the pump is going bad but not dead yet. It's a "real" Bosch 044 so I'm a bit disappointed (lots of counterfeit 044 pumps out there, already had one go bad), but have ordered another, this time from a Bosch retailer with a lifetime warranty!

Two things... can I use a multimeter to test the pump and see why it has lower voltage? Am I barking up the wrong tree? I checked all my connections etc for power and all were fine until the pump. Also look at the crud that I cleaned out of the pumps' pre-filter... its a small fabric filter that fits on the intake end of the Bosch. I cleaned it with carb cleaner cause it looked brown. That is from fuel that is already filtered by the swirl tank pumps' inline filter that then fills the small "swirl" tank the Bosch is in that then supplies 60lbs of fuel pressure to the injectors (there's another much finer filter after the Bosch fuel pump too, so no worries). I wonder if this contributed to the early demise of the Bosch? The clear liquid is carb cleaner, then another pic after it had evaporated down. Thoughts? Glad this happened BEFORE dyno day in July...

[Stick]

Hey, Greg. Wish I had some answers for you regarding a pump test, but I'm not all too familiar with that pump. I would think it would be pretty simple 12v in and similar out with a regulated pressure/flow.

I would suspect that the contamination could take a toll on the performance and potentially cause an early demise if too heavy. might be worth draining and cleaning your tank at some point or adding some finer filtration prior to the pump?

Hope you get things sorted out!

Greg

[Habitat.pat]

Greg, since I’m not familiar with your specific set up, I’ll address basic electrical troubleshooting.

I assume that there is a relay or solid state controller between the pump & battery. Has any of the wiring been changed recently? The wire between the pump & battery should be at least 16 ga.,I’d probably use 14 ga. Do you have a roll over switch? If so, where is it in the circuit? (This is more of a rhetorical question just to be sure you aren’t overlooking a component).

First of all, your low voltage is not normal but may have wthat way for some time. In looking @ the pump specs, it shows that the voltage should be above 12.5v & the pump should draw about 13a.

There are several troubleshooting methods but I prefer the successive division approach, start in the middle, then move one way or the other until the problem is found. All these tests need to be with the pump running. Check the battery voltage to ground. Assuming you have a relay in the circuit, measure from the wire to the battery, it should be close to battery voltage. Since you are there already, check the voltage out of the relay, it should be the same. If the voltage is good, check @ the pump again, if it’s low, I suspect that the wire is damaged or undersized.

If the voltage @ the relay is low, measure the voltage @ the fuse that feeds that circuit.

With the different voltages with the 2 pumps, I suspect a bad relay, connection or the wire is too small allowing the 044 to not get enough power or the pump is pulling too much power. If you have an ammeter, you can connect it in series to check the draw.

Feel free to ask as many questions as needed. Good luck.

Peace, Pat

[jhayden]

Does your MicroSquirt have a Schrader valve that you can hook up a pressure tester to? If so, Snap-on makes a tester that is a worthwhile investment. The LT1 runs 20 micron filters before and after the pump, and requires 40 psi minimum.

I'm with Greg M on the need for clean fuel: efi in general is less tolerant of contamination than carbs. I clogged the first set of injectors before removing the tank and having it cleaned and coated (we are fortunate still to have a radiator shop locally that serves the vintage auto community). Zero problems for about eight years now, and running only non ethanol gas with Sea Foam.

Good luck -- looking forward to seeing those Dyno numbers next month.

Jon

[redroadster]

The neg wiring to the pump ,any other component hooked into it? I'd run another wire to it jam it up the connector to see if it changes the readings a big load will drop voltage but 9 seems low . Possibly the pump has a malfunction if you use additives it can affect the rubber impeller stiffening it on electric motors if you turn down volts it raises amps ,if you amp clamped it it would help to know
Neg and pos sides amp draw , might try a new relay ,is it on the neg side ?
If you have an exhaust leak even tiny before the check O2 it gives a lean condition . Try hooking a simular load electric mtr in place of the pump mtr.
to see what Vs it reads

[Gregs672000]

Thanks for the responses! Voltage checked out fine at the relay and at the terminals/wires that power the pump, but when ATTACHED to the pump would show 9 volts at the pump itself. The low pressure pump runs on a separate circuit and is not involved in the electrical system for the bosch/high pressure pump. The bosch pump also sounded different, not sounding as strong on the priming run as before (I can flip the power switch on and off to cycle the pump with the engine off over and over). Can I hook up a multimeter to my pump and check some kind of resistance that might suggest it's having problems? It's out and on the bench.

Yes, I was very surprised to see that cloud of crud... my tank has always been pretty clean. There's a typical inline filter ahead of the low pressure pump that pulls directly from the gas tank, then that fuel is sent to the swirl tank that houses the Bosch high pressure pump, and that's what had the fabric filter on the intake end and where all the crud came from. That then goes through another small micron filter for EFI systems after the Bosch, so I don't expect that anything is reaching the injectors. The fuel return line does go back to the swirl tank, but by that time it's gone through 3 separate filters and the entire system.

Thanks all! I'm nieve when it comes to electrical stuff.

[Habitat.pat]

Where is the relay located?
With the pump hooked up & running, what are the battery voltage & the voltage @ the relay?

Voltage readings without the pump running will be close to meaningless.

[redroadster]

If your checking pos wire @ 9v it is a normal condition .
the 12 DC current is pulled to the pos batt post .that means your reading It after powering the 13a pump .to accurately check power to it chech the neg side , to pos on the meter
Anyone that thinks 12 DC current flows from the pos will never understand 12 v electronics unless its backwards. They used to make a short detector that you held up to a elect.wire and the needle showed the flow direction

[Gregs672000]

Where is the relay located?
With the pump hooked up & running, what are the battery voltage & the voltage @ the relay?

Voltage readings without the pump running will be close to meaningless.

Aw, bummer. No way to run it now that I pulled it. The relay is located under the dash on its own board with the fuse box for the injectors etc. It had 11.50+ volts out to the pump without the engine running as I recall, 12 volt power in from the battery so no significant drop there as I recall. I need to take a look at it again to see how I wired it, but it's been fine for several years.

So seeing 9 volts at the pump was not an indication of a pump problem? Any idea why the (new) cheap "back up" pump showed 11+ volts when hooked up? That's what had me thinking "it's the pump...".

[redroadster]

You will see 12 v ( battery voltage ) at the pump , on the front side , which is _____ ?
Lower amps, capacitor differences on your ? ...HF has a $23 amp clamp, you should have / test with ...put on both batt cables while cranking ,you may be shocked ..ha

[Public_Impressor]

Testing with a multimeter to check voltage at the pump is key here. Lower voltage under load could indicate a wiring issue. Cleaning out the pre-filter was smart; dirty fuel can affect pump performance.

[Gregs672000]

To close out this post, turns out it was most likely a ground wire issue. I run the ground for the main fuel pump to a dedicated "port" on the battery terminal and it appears to have not been making good contact. Of course, I purchased a new Bosch pump, so I'm deciding on returning it vs keeping another back up, but after fixing the wiring and checking the old pump I reinstalled it and all is well. I kinda jumped the gun with the new pump but didn't want to miss my dyno appointment next week. The good thing is I did get to clean out the swirl tank and the pump pre-filter... so glad I put that on there! Attached is a pic of the crud after all the carb cleaner evaporated away. Looks chunky but it was really very fine material. Doesn't look like a lot but considering it had already gone through one filter I was surprised, and it's nothing I wanted heading toward my injectors! I kinda doubt typical injector cleaner would break it down completely, it's pretty hard stuff. The 100 micron filter after the main pump should catch anything else. A click on the Pic and it will be right side up...

"Scott to bridge, warp drive reestablished..."

[redroadster]

That's graphite colored, the brushes are made of that usually or composite
Is this a wet pump ( gas goes over the armature )

[jhayden]

Greg, only b/c redroadster re-opened this thread will I now get this off my chest:

It seems highly unlikely that you will be satisfied long-term by relying on 100 micron filter(s) to keep an efi system going behind an untreated fuel tank that is approaching sixty years old. Borderline satisfactory for a side draught setup of whatever type (SU, Mikuni, Dellorto, Weber), but not modern efi. A general rule of thumb with a clean tank is a 100 micron element filter before the pump, then a 10 micron filter before the injectors.

You'll probably be fine for your Dyno run coming up, but pulling the tank and a professional treatment will be well worth your time and effort.

Again, I was holding back with this ha'penny worth of advice, but now you have it, and hopefully it won't offend you. No one on this forum has been more forthcoming with help than you.

Jon

[Gregs672000]

Jon, I absolutely appreciate your and anyone else's input... I may talk a lot and love my car but my ego is generally in check! I'm no expert on anything, just doing my best to learn and share eh? We have the same goal in mind... keep Greg's car running !!

I will take a good look at the tank as well as what additional filtration may be prudent. So, 10 micron before the injectors eh? Here I thought that 100 sounded super clean!