98 Escort, fuel pump not running..

[mightymoose_22]

Wow... some very, very thorough stuff here.
My two cents...

You mentioned the appearance of the fuel on the pump side when you replaced the filter... after having the tank removed and who knows what done to it... I wouldn't be surprised if things got sludged up and the pump was simply clogged. In the process of removing it and all the tinkering perhaps it became unclogged and decided to start working again

I would be very concerned about my fuel supply if it ever came out looking like you described. If it happens again then you might want to take a better look at the condition of the fuel in the tank and find out what kind of gunk it might be sucking up out of there.

[dllewell]

For the last 2 days, the car has been running fine...though i am still cautious ans now i carry all the necessary equipment to connect the pump directly to the battery in case it needs another 'jump'.

Both of the last 2 posts mention the recent work i have had done to the tank as well as the obvious sludging at the filter.

The line follows: tank-strainer (mesh)-pump(in tank)-filter (bolted to firewall)-engine. As such, there is a high likelyhood than any swarf (i love that word!) couold get into the pump...in fact i am leaning towards this possibility.

Now the tank had pinholes in it and when it was repaired, the rotten area was cut out and fresh metal was welded in. Then the tank was coated inside and out with some sort of epoxy.

In order to do any welding on a tank, they have to wash it out pretty good... so i imagine it was pretty clean but who knows what was still in there when it was reinstalled. Furthermore, perhaps the mechanic installed the pump improperly (like without the screen, or there is a rear in the screen.) I wont know unless i pull er out.

My brother-in-law, who is a mechanic has also suggested that letting a pump sit dry for a while can bugger it up as well (whenever he removes a pump he always seals it in a container with some gas). Chances are that my pump sat out on a workbench for at least 24 hrs.

He has recommended that i replace the pump, but without clearly knowing whether it is a mechanical blockage or an electrical issue i am hesitant to spend the dough (aftermarket the pump is about 250$ Canadian).

Thanks for the lesson on back EMF Selectron

D.

[Selectron]

I'm pleased to read that it's still running well. I've been thinking about the age of the car - 1998 - if the fuel pump had a dead spot then it's had plenty of time to show up before now so I've moved away from thinking of that as being a likely cause.

I think it's too much of a coincidence that this has happened just a short period after the tank repair so I go along with what mightymoose_22 said, and my best guess would be that either a piece of debris or just a build-up of sludge has brought the pump to a standstill (not helped by the corroded connection at the battery terminal).

Hopefully, the worst of the sludge will by now have made its way through the pump and been caught at the (now discarded) fuel filter, and hopefully from here on in the fuel system should be cleaner and more reliable. However, given that this problem took one month to show after the tank repair, I'd be tempted to remove the fuel filter again one month from now and take a look at the input side and see how it compares in terms of cleanliness to the one which you just replaced - hopefully it will be a big improvement but if not then you will know that you have problems back at the tank and you may be able to do something about it before the system fails again. I know that you said the filter is awkward to access but I'd say that it would be worth the effort just so you can get an idea of the state of the fuel system.

[dllewell]

Last night i did some electrical testing:

Battery:
1. sitting 12.8 V
2. key in run position 12.4 V
3. cranking to start 10.5 V
4. car running 14.2 V

Fuel pump:
1. key in run position 8.5 V, 4.0 A (drops to 0 V, 0 A)
2. cranking to start 7.6 V, 4.0 A
3. car running 7.6 V, 4.0 A

When i open the throttle (step on the gas) the running voltages for battery and fuel pump increases, however the Fuel pump Amps remains relatively constant.

Remember that i did see upwards of 10 V to the fuel pump at least once, but now it seems to be quite constant...and its roughly but not quite half of the running voltage of the battery.

This surprised me. Perhaps the FP is not meant to run on 12 V. Or perhaps there is another reason for the Voltage drop (other componentry, poor wiring, bad ground?). I wish i could measure someone else's car!

D.

[12Ounce]

My diagram (for the '97) indicates that the fuel pump is to get a full 12 volts. You have something impeding current flow. You mentioned a blown fuse ... maybe it blew from heat from a dirty base ... not from current flow. Perhaps a dirty relay contact or base.

I would start out at the fuse #15, measure both sides ... and then step back through the wiring all the way to the pump. As soon as the voltage drops away from the battery voltage, you know you are close to the problem.

Fuse #15. .... to
BL/Y wire to ter #11 on CCRM. ...to
Fuel Pump Relay. ....to
Ter #5 on CCRM to INERTIA FUEL SHUT OFF SWITCH via BK/PK ...to
1)INERTIA FUEL SHUT OFF SWITCH to ter #5 and ter #6 Fuel Pump (module) via BL. ...and to
2) FUEL PUMP DIODE via BL.
.
Both the diode and the pump are grounded thru BK. The diode, in electrical "parallel" with the pump, seems to be harness mounted near the pump.
.
Good luck.

[Selectron]

Excellent input there from 12Ounce, which I'll add a few comments to, all based on the assumption that the pump should indeed be fed at the full supply voltage, which with the engine running you have measured at 14.2V

The reading taken directly across the pump connector is 7.6V so you have lost 6.6V somewhere in the circuit, due to either a fault condition or a high-resistance (corroded) connection. My first step would be to determine which side of the circuit the loss is happening on - the incoming feed from the battery positive, or the return path back to the battery negative, because it could be on either (this is what carlos80 was referring to when he talked about 'backprobing' in both directions).

It would make things easier if you had a length of wire maybe 12' in length, with which to extend the physical reach of one of your multimeter leads (just one - not both). If you have that, then I'd advise the following (all readings taken with the engine running):

Measure voltage at fuel pump connector and verify that it's still 7.6V

Now place the meter negative lead onto the 12V positive feed terminal at the connector, and extend the meter positive lead back to the battery positive terminal and, probing directly onto the terminal post, take a note of the voltage.

Next, remove the extension lead and connect the meter positive probe directly to the fuel pump negative connector, and this time extend the meter negative lead back to the battery negative terminal and, probing directly onto the terminal post, take a note of the voltage.

As carlos80 said, you should expect to find little voltage on either side - say 0.5V maximum. However, we know that you will find 6.6V on one side or the other, or perhaps the missing voltage will be split across both sides.

If you find 6.6V when measuring back to the battery positive terminal then your problem is in the supply feed side of the circuit and you should start probing back through the feed path - that path being battery positive to relay to inertia switch to 6-way connector to pump. Somewhere along the path will be a fault or a high resistance connection of the order of 1.65 ohms, and we know that because:

resistance = voltage / current
R = 6.6V / 4A
R = 1.65 ohms

If, on the other hand, you find 6.6V when measuring back to the battery negative terminal then your problem is in the negative return side of the circuit and you should start probing back through the ground return path - that path being from the pump 6-way connector ground terminal, to the bodywork, to engine block, to engine grounding strap, to battery negative terminal. Somewhere along the path will be a fault or a high resistance connection of the order of 1.65 ohms (same calculation as above).

If there is a problem in both the feed path and the return path then you may find, for example, 4V on one side and 2.6V on the other side (but totalling 6.6V), in which case you will have to probe back through both the supply feed path and the negative return path in order to locate both of the high resistance connections, because there will be one on each side.

One thing has just occurred to me, which is that if you have dirty relay contacts then they could be causing this. I'm not talking about the externally accessible terminals, but the internal conductors which actually make and break the circuit - if they are dirty or pitted then they could be causing the voltage drop. This, however, would be revealed by probing the feed into, and the feed out of, the relay - the output side would be 6.6V lower than the input side.

I hope you follow that and I hope it will be of some assistance. Any questions, just ask.

Edit: Just to clarify - when I talk about probing back looking for the high resistance connection, I'm not talking about taking resistance readings on the resistance range of your meter, because you cannot take resistance readings on a live circuit. Rather, I'm talking about taking voltage readings, and if you found, for example, a certain voltage going into the relay but a lower voltage exiting the relay, then that would, by implication, reveal a high-resistance contact - the readings would all be voltage readings though.

Edit #2: I just remembered that your battery is in the trunk (mine is under the hood). This makes things easier because you shouldn't need to extend the meter lead by any great length. Also, your negative return path will presumably be from the pump 6-way connector ground terminal, to the bodywork, to battery grounding strap, to battery negative terminal in trunk.

[dllewell]

WOW, again excellent suggestions, and very well written, i understand completely. My grandma died yesterday and i am off halfway across the country to the funeral, back Tuesday. I will try this tonite but if i dont get to it then please check back here mid-next week and see how things went.

3. points: I still dont know where the fuel control relay is located, i was hoping someone would catch that in earlier posts and offer some helpful advice.

the battery is indeed under the hood (front of the car) but i can find an adequately long wire for this testing.

One of the wires at the fuel pump actually is grounded to the body of the car right there. However, this is not apparently the gorund for the fuel pump circuit. According to the circuit diagram, the return wire goes back to the fuel pump control module...and then to ground i guess

thanks, D

[Selectron]

Sorry to hear about your grandmother. I hope you will have a safe and uneventful journey.

I'm wondering now about that fuel pump control module. I'm reluctant to introduce a hypothesis in case it muddies the waters but now that I've thought of it I'd better mention it in case it proves to be relevant. Consider this: with the engine idling, fuel consumption and therefore fuel flow rate will be minimal, so not too much effort will be required from the pump to keep the fuel system up to normal operating pressure. However, when driving at speed along the highway, fuel consumption and flow rate would be considerably increased, and I wonder therefore if this is a smart module with a feedback sensor, which can adjust the fuel flow rate according to the current driving conditions, by varying the voltage applied to the pump - reduced voltage at idle, increasing towards full supply voltage at greater speeds.

If that were the case then it could explain why you have measured the voltage at the pump (whilst operational) at both 7.6V and at 10.5V - perhaps the reading at 10.5V was taken after you had disturbed the fuel system so the pump would be working harder in order to refill the system and regain normal operating pressure with, perhaps, the supply voltage falling back to its idling voltage of 7.6V after the system had been re-pressurised.

That's all hypothesis, and I may be forcing the recorded voltage readings to fit in with a theory but it is a possible explanation of why the pump voltage might legitimately fluctuate intentionally, by design. Unfortunately, I can't prove or disprove it for you because my Escort is diesel-engined.

I would recommend that you measure the voltage, as outlined earlier, from the 6-way connector positive terminal back to the battery positive terminal, and then from the 6-way connector negative terminal back to the battery negative terminal. You will then know on which side of the system the missing 6.6V is being lost and you can then set about identifying which section of the system it is being lost in.

Yep, I'll check back for sure because I'm keen to know what the final conclusion will turn out to be.

Meantime, if anybody reading this has any knowledge on that fuel control module/fuel control relay - its operation or even its location then that would help a lot. Thanks.

[Selectron]

Double-posting here so read the post above this one first if you haven't already seen it.


You know what? I think my hypothesis is the answer - I think the fuel pump is designed to run from a variable supply voltage - varying according to current driving conditions. There is a clue in your earlier post (post #19):

"When i open the throttle (step on the gas) the running voltages for battery and fuel pump increases, however the Fuel pump Amps remains relatively constant."

The battery voltage increase will just be an increase in voltage output from the alternator - that is to be expected so don't pay any attention to it. The significant point is that when you open the throttle, the fuel pump driver control module responds as we might expect - it increases the voltage to the fuel pump to keep pace with the demand for more fuel.

I did a search on Google and I found the following. It isn't from a technical article - it's just something which somebody quoted on a forum elsewhere, referring to a '98 Escort with a fuel supply problem:


Fuel Pump Driver Module
The fuel pump driver module (FPDM) receives a duty cycle signal from the PCM and controls the fuel pump operation in relation to this duty cycle. This results in variable speed fuel pump operation. The FPDM sends diagnostic information to the PCM on the fuel pump monitor circuit. For additional information, refer to PCM Outputs, Fuel Pump and PCM Inputs, Fuel Pump Monitor in this section.


In light of that, I wouldn't even bother taking any more voltage readings, because I suspect you're chasing a fault which doesn't exist - I think the voltage varies by design and that's all there is to it. Provided that the vehicle performs well at higher speeds (high fuel flow rates) and provided that the engine is not hesitating and shows no signs of being short of fuel, then I don't think you need worry any further, beyond of course bearing in mind that the contents of the fuel tank remain in question, because it was almost certainly debris or sludge from the tank which caused the initial malfunction in the fuel pump. Beyond that though, I don't think you have anything further to worry about.

[dllewell]

Thanks yet again Selectron,
It would be truly helpful to have another one of these cars to compare with!

I had, in fact, considered the possible of variable voltage (not seriously though). I believe that some DC motors are much more capable of handling variable voltage than AC motors (perhaps a gross generalization).

I cannot hear the 'speed' of the fuel pump while running at speed, but theres nothing stopping me from hooking the multimeter up across the pump leads and observing how increased loads (fuel requirements) affect the voltage. (i will have to extend the leads of the multimeter a bit to make this a safe venture.)

This, too will have to wait till next week.

cheers, D.

[12Ounce]

I'm sorry to hear about your loss. I never knew any of my grandparents, I was born too late.

Don't get caught up in Ford semantics. The "fuel pump module" on your model is that thing in the tank. It supplies fuel until an internal pressure level is satisfied ... that is, as long as it gets a 12 volt source. I think there is a primary pressure regulator right there at the pump, and of course, the secondary vacuum-assisted one on the fuel rail.

In "Ford Speak" there are "door control modules" ... use to be "door regulators", etc, etc. ... all kinds of "modules".

On later Ford models, there is no return fuel line from the fuel rail to the tank ... then control items get a little trickery. More sensors. Different power forms. Does your fuel rail have the regulator and return fuel line on it?

[dllewell]

12Ounce:

there is only one fuel line attached to the pump itself, however there may be a return line that goes directly to the tank, at least this has been suggested to be the case.

so you recommend that i dont go poking around under the dash for this mysterious control module?

furthermore, this would be contrary to Selectron's theory that the fuel pump is controlled by variable voltage. care to comment?

I dont know what to look for under the hood in terms of a regulator/ return fuel line on the fuel rail.

I still plan to hook the multimeter up and go for a drive and see how load (fuel requirement) affects the voltage across the fuel pump.

I am also very tempted to try to find another 98 Escort at a used car lot and go for a 'test drive'...ie. back to my garage for the multimeter test.

d.

[12Ounce]

I don't have a diagram for '98, but I do have one for '97 (somewhere, can't lay hands on it at the moment). The '97 is very straight forward ... 12v is shown at the in-tank module. I would be very surprised if the '98 changed this feature that much...but would not bet on it!

The "secondary" (my term) regulator is mounted right on the fuel rail that feeds the injectors. At the belt end of the engine. It has a small vacuum hose attached. Do you see this gadget?

Your idea of comparing another '98's voltages is right on target!

[dllewell]

OK, finally did the fuel demand vs. voltage test.

Hookekd the multimeter to the 2 leads feeding the fuel tank and went for a drive. The voltage definitely varies. It varies from 6.9 to 9.9. At idle, the voltage is pretty much stable at 7.4 to 7.7. On the road, the voltage increases during acceleration or while trying to maintain the same speed while going up hill. If i let off on the gas, push in the clutch or even gear down (to slow down) the voltage generally drops, and it drops right away.

It is now clear to me that voltage is tied to fuel demand (engine load). It is not specifically tied to engine speed or road speed. You can gun the engine under no load (neutral) or low load (first gear) and the voltage doesnt go up that much. However, i did accelerate up to about 100 kph in 3rd (uphill). I dont have a tach but based on engine noise and vibration i'm guessing that i was up between 5500 and 6000 rpm. This is when it hit 9.9V. (i suppose i could calculate the engine speed for a given gear and road speed...knowing the gear ratio and tire diameter).

So what do we know now thats new? Voltage varies (proportional?) with fuel demand. I was however disappointed that it only got up to 10 V, even at 140 kph. Not disappointed though, that there is no apparent hesitation at this speed, suggesting that the fuel pump is capable of keeping up with fuel demand.

as for 12Ounce's info on the fuel control module. The 97 and 98 are completely different according to the wiring diagrams in Chilton. I am still hoping that this variation in voltage is by design. And if so, I assume that the fuel control module is to blame...hence it is located somewhere upstream of the wiring harness that connects to the top of the fuel pump (and not inside the tank with the pump).

so far unable to get my hands on another 98',

still considering backtracing the circuit as well...but i need to know where this darn fuel control moduel is!

D.

[Selectron]

Welcome back, dllewell. I've been following the thread but I didn't really have anything to add. Well, reluctant though I am to disagree with 12Ounce (and I'll be happy to be proven wrong on this, just so long as we solve the mystery!) I have to say that that does look like a variable-voltage pump. You've taken a comprehensive, meaningful set of readings, and all of them point towards the voltage varying by design. I say that because:

• Voltage increases under acceleration (as one would predict)
• Voltage increases under increased load (hill climb - again, as one would predict)
• Voltage decreases under deceleration (as one would predict)
• No engine hesitation has been observed

At engine idling speed, the battery voltage may fluctuate somewhat, probably at thirteen-point-something volts, but shortly above idling speed, the voltage regulator will take over and clamp the voltage at 14.2V (as recorded earlier in this thread). Therefore, with the voltage firmly clamped at 14.2 volts, there is no reason for the voltage at the fuel pump to be fluctuating, unless by design. Even if there were a fault condition which caused it to fluctuate (e.g. a connection which was both corroded and also loose), it's beyond the bounds of probability that the voltage fluctuation would mimic precisely the behaviour which we would expect to see from the feed to a variable voltage pump.

As for being disappointed that the voltage only reached 10V, and not the full supply voltage, I would make two points.

Firstly, if it's a variable-voltage pump then it would not necessarily follow that the upper voltage limit would be set at the same level as the full supply voltage - the upper voltage may have been determined by electronics circuit design considerations within the control module.

Secondly, although you are only seeing an increase in voltage of around 44%, from 6.9V to 9.9V, that is only half the story. Bear in mind that along with the voltage increase, the current flow will also increase and therefore the power dissipated at the pump will increase - but by more than 44%. I'd guess it goes something like this:

6.9V x 4.0A = 27.6W
9.9V x 6.0A = 59.4W

So, although the voltage at the pump only increases by less than 50%, the power (wattage) at the pump increases by around 100%, i.e. it doubles. That looks a lot more reassuring eh.

All things considered I'd still come to the same conclusion as before - the pump is variable-voltage by design, and probably (although we have no way of proving it) operating within specification (because you have no reason to believe otherwise, because the engine performs well at all times) and the problems have all been caused by physical contamination within the fuel tank following the tank repair.

If you still want to investigate further, then I'd suggest you do the two checks which I outlined in post #21, measuring first the voltage between pump connector positive terminal and battery positive terminal, and then the voltage between pump connector negative terminal and battery negative terminal. On one side or the other - probably but not necessarily - the positive side, you will get a reading of around 6.6V - in the event that the pump is indeed variable-voltage then this tells you which side the control module is on and you can set about locating it by taking voltage readings along the electrical path. Or, in the event that it's a fixed-voltage pump intended to be fed at full supply voltage, then it tells you on which side of the circuit your fault lies and you can set about tracing it.

There is one exception to that, which is that the pump may be fed from a dedicated, isolated supply, in which case the voltage will be 'floating', meaning that it will not be positive with respect to battery negative, nor negative with respect to battery positive, but just electrically floating, in which case you would get nonsensical readings when taking the voltage readings in post #21. That would be a complex piece of design though and I doubt that is the case, but if you get completely unexpected, illogical readings then that would almost certainly be the reason why.

The only hint I have as to a possible location for the pump driver module (if it actually does exist) is a snippet which I found which refers to a '98 escort sport', whatever that may be. It says The fuel pump drivers module is located inside the vechicle, behind the Left hand wheel housing. It's on another forum and it would probably be impolite to be posting links to other forums here so I'll send you the link via PM.