01 Focus Fuel Pump Testing With Fpdm
Hello, let me start by saying I do not have much experience with scopes and I have not scoped but a couple of fuel pumps. The customer took his focus to another shop with the complaint of intermittent hesitation and some times it would stall out. The other shop looked at it and fired off the old parts cannon installed new plugs, wires, and a coil. That did not fix the complaint. when I received the vehicle there was one code P0304. upon looking at the freeze frame data I noticed the FRP was reading 18psi. when I test drove the vehicle I managed to get the FRP under 10psi at WOT. so obviously this is a fuel related problem. However, the vehicle is equipped with an FPDM. When I scoped the fuel pump I grounded pin 3 on the module which completed the circuit for the fuel pump, bypassed the module. The current waveform shows 11,000 rpm??? whats your thoughts? How should I go about testing the module? and the PCM driver?
I think you are putting your cursor in the wrong spots. Post the pico file. What was the fuel pump driver module duty cycle command when the pressure dropped? Does the pressure still drop with the bypass in place?
here is the pico file and a recent scan data I drove the vehicle with out the bypass and then pulled off and connected the bypass. pressure still drops when bypassed
If it’s still dropping below spec with the driver module in bypass it has an issue in the pump area.
Dead head the pump at the fuel rail and bypass the driver module and see what pressure you have.
I uploaded a more complete scan data. ill try this tomorrow but with the bypass connected driving down the road fuel rail pressure still dropped
Yep bad pump . If power and grounds good. Have done a lot of current ramping and that pump is not right
Yea I'm concerned with the power side ill check it tomorrow. with the key on engine off with the bypass connected voltage was down to 10.5v key was on for 30mins or so. But was up when I started the vehicle. I'll double check that tomorrow.
You will get mis fire codes with low fuel pressure . This is not a healthy pump . If you want to be sure do a dead head pressure on the pump like was mentioned before but see what your amp current is . This will tell you for sure
I think that, like most pumps, this is an 8 segment pump. I used the negative tail(s) at 373 and 384ms on the larger capture picture. That would make the pump more like 5500, which is pretty normal. I questioned why the fuel trim is near 0 with only 18psi fuel pressure at 76% engine load.
Yea I see were I was off on the measurment do you always look at the negative tails when looking at fuel pump current. As far as taking fuel away. When It acted up on my test drive the trims went high.
Negative trims or positive trims. And what was your injector pulse
Positive trims SFTRIM 21 FUELPW1 (MS) 63.5
Yep low fuel delivery
So when a vehicle has a separate fuel pump module like this do I need to bypass the module to get a good current reading as I did here? Even when I can command the fuel pump to %100 with a scan tool? Can I get a good reading with fuse loop when it has a module like this? What is your diagnostic process?
Check at pump . But your scope pattern on pump is no good
Disconnect FPDM connector and jumper the pins. B+ to pump+ and GND to Pump- Typically I deal with tow-ins, so I do that first, and if the pump doesn't run I'm done. If the pump does run then I could current ramp right there and do further electrical testing as necessary.
Thanks for the input. I had one bite me about a month ago. a Toyota tundra similar complaint as this one. it has an FPDM above the rear axle. by the service manual, you should install the scan tool to put the pump to %100 and watch fuel pressure. I did and it hit 55psi which was just under the recommended pressure. watched for the leak down it was good. current ramped the fuel pump (which as you…
I've never dealt with a Toyota system, I was speaking specifically of these older Fords. Ford usually sets DTC too. But the DTC "name" in the Scan Tool can be deceiving if you don't actually read up on it in SI. Like "no message from driver module" or something, that might make someone suspect the FPDM is bad when really it's not going to send a message if the fuel pump has failed. Just extra…
Nathan, Stephen is right, 8 segment pump, running somewhere between … rpm. Look at the signal, one or more of the segments will always have a signature to its current ramp. In this case, the ramps are such a mess that it's easier to pick out the repeating pattern. See the high segment at 380.7ms in your zoomed out screen grab? It is there again just before the 391ms mark. Not only is it…
Yep signature pattern on pump is were you want to go . If you scope it at pump with good power and grounds pump with this pattern will cause a problem . Over 25 years current ramping pumps im no trainer just saying .
Your current waveform of the pump is pretty conclusive. Bad pump.
I'll start this with I am no expert when it comes to waveforms, but I am curious about this. This era focus had a history of failing fuel pumps. There were warranty extensions and fuel tank modifications for this. I remember there was a note in the owner letter (recall notice) about keeping the tank over 1/2 full to keep from stalling. 1/2 tank was enough to keep enough of the pump housing…
On certain passenger vehicles, contamination of the filter in the Fuel Delivery Module (FDM) can reduce, and eventually block, the flow of fuel to the engine. CONSEQUENCE SUMMARY This may cause engine hesitation, loss of power, surging, and other similar driveability symptoms. Over time, the filter may become sufficiently blocked to cause the engine to stall, which could cause a…
Might be, I just remembered about people being told to keep their tanks over half full to keep the pump from overheating. Might have been fake news and the higher fuel level may have let more fuel into the housing if the filter on the bottom was restricted. I do know the clogging filter issues were resolved with a redesign of the pump which required the retaining clips to be cut from the bottom…
for future reference, I have another question as you all can tell I was off on my RPM measurement. However, there are 8 humps there if you count the little humps. What would you say the little ones are?
Just me thinkin’; I think the little humps are the result of brush contact loss. At the bottom of a big hump it turns up and has the curvature of an inductive load as it increases. Then falls, almost straight down, then recovers and continues up. If a line is drawn in to bridge the negative drop, the pattern looks more normal. The little hump blends in to be the beginning of the big hump. I…
Thanks, everyone for the help. I sold a fuel pump, but it will be a day or so before I can change it out. I will retest after and post new scan data and a new waveform. I still have some questions but I will wait till after I change it. Thanks again.
Check out you tube video on this subject fordteckmakuloco a great ford teck
Nathan, while it seems you have a handle on it with the fuel pump, I just wanted to point something out in case you didn't know. FRP sensor does not equal actual mechanical pressure on a running engine. FRP is referenced to manifold pressure and mechanical pressure of an actual gauge is referenced to atmosphere. Just something to keep in mind in the future.
thanks, James I did not know that. but still ok to use for diag? just verify results with a mechanical gauge?
Nathan, with engine off the readings should be close together. I'm sure there is a formula for converting while running taking into account MAP, but I'm just use to always using a mechanical gauge and have built adapters that go inline for anything I don't already have one for as needed.
ok, guys I finally got this pump in yesterday. Here is what I got before I installed the pump pulling the vehicle into the shop it would hardly accelerate. Hooked up fuel pressure gauge 7.1psi was all it had. after install it put out 42.2psi at idle. Dead headed new pump 99.1psi. WOT throttle down the road FRP was at 39psi. The waveform was really messy and needed a filter. I put the old pump in…
New motors will usually have a rough pattern. I believe it’s because the brushes need to wear a little before you will get a cleaner capture. As others have mentioned here the pid for fuel rail pressure is not an exact transducer measurement of fuel rail pressure. But for me it’s close enough when I see something as far off as you saw here. I haven’t seen one that was skewed off from actual…