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I started to map my FD some months ago with the oem fuel pump. In the meantime, I had to fix some details and I also upgraded the fuel pump with a Walbo 255.
Today, we continued the mapping but after the first test runs, my mapper told me we had to stop because the fuel pump was worse than before... the mapping was now leaner than before and he had to raise a lot the fuel quantity to compensate, and eventhough the injectors duty reached 102% long before redline... He told me to put a bigger pump.
I was wowed, because I thought the 255 was enough for my "humble" setup (PFC, 10psi, SMIC, DP/HFCat/Catback in 3", and Water Injection. Stock injectors, stock FPR and new fuel filter)
Can you confirm this pump is ok for my setup ? (I definitely don't need more than 300hp)
Maybe I've done something wrong during the install ? How can I check that I mounted the pump correctly ? Should I install a fuel pressure gauge to check the pump's efficiency ?
Should I do the FP hard rewire ? I checked voltage at the harness on top of the pump, it was pretty good (13,8V, engine off)...
Can the Fuel pump resistor be in cause ?
I don't know what to do first, and how to be sure it's OK before I go the next mapping session
(please pardon my bad english, but I can't edit the title to correct "worse" )
yep, thanks
I assume it's a true one, cause I bought it on a very reputable website here in France, they confirmed they are coming directly from Walbro. But, I found this website earlier, on how to spot fake and real ones ! So I'll definitely check if it's a real one or a fake ! https://www.driven2automotive.com/bl...pumps-2017-18/
I don't have much to add here except that measuring the voltage at the pump with the engine off is not an indicator of voltage drop.
Voltage drop over a fixed resistance increases proportional to current flow, meaning your measurement of 13.8V while the engine is off could drop significantly when the pump is on and trying to keep up with the engine's needs in-boost.
My car's previous owner did the fuel pump rewire so I don't have any personal before-and-after experience. But I figure if its within your ability to do it can only help. Good luck!
yep, thanks for your advices !
I didn't know how to measure the voltage while the engine is on with the FP harness connected, I have no access to connect wires... I'm also considering to activate the pump out of the tank (engine off, using the diagnostic box) and check the voltage directly on the pump...
Anyway, I'll probably end up doing the FP rewire.
step one is to see voltage at the pump, you would measure the battery volts, and then with the pump unplugged, measure the voltage at the pump. it should be within about 0.5v, if it is not, then you need to check the ignition switch, relays, etc. there is a rewire that bypasses the ignition switch, and that is a good idea, it reduces the load on the switch, etc.
step two is to measure voltage with the pump running. the pump takes voltage to run, so voltage with the pump running will be lower. something like 2v lower. if its using more power than that, something is probably not right.
since fake walbros are a thing, pulling the pump and making sure you have a genuine unit is a good idea
A genuine Walbro 255 will definitely do the job of 10psi. I ran my twins on that pump at 12psi for quite a while but my car was re-wired because I didn't trust the fuel pump resistor system. I would try a re-wire if you end up having a genuine unit. Maybe consider injector cleaning if you premix or the job has never been done before.
I had an 255 years ago and was not impressed. I don't know if mine was worse than the stock pump, but it certainly wasn't much better. We swapped it in when on the dyno and it didn't improve fuel pressure much at all at the top end. That pump went on to live in my old Volvo 850R when its pump failed. I'm not sure what the current good pumps are, but I put in a Bosch 040 and that was many times better than the Walbro 255.
Moral of the story is I wouldn't recommend the Walbro 255 to anybody unless they were looking for an affordable stock replacement.
I'm a fan of the Walbro 255, again you do have to be certain you have a real-deal pump as the knock offs (of which there are MANY) can underperform.
Care also needs to be taken when installing it so it's got a solid seal to the outlet tube in the tank. If the o-ring isn't sitting or sealed right you could have pressure leaking back into the tank.
I would cut off the stock pump tube end with the plastic crap on the end of it. Replace that with SAE30R10 submersible fuel hose.
Also, check the connectors and pins at the hanger bulkhead connector, especially the ones inside the tank. Had a major voltage drop on mine and bypassed the stock bulkhead connector. https://photos.app.goo.gl/AVRpAZFVvJjf6Nbv5
For what it's worth I have been pleased with my Aeromotive pump up to 15 psi of boost running 2200 secondaries.
I would install a fuel pressure gauge. I like mine for keeping an eye on fuel system health when I log.
As far as wiring goes I haven't needed anything more than the ignition switch bypass that Dale detailed a while back. Stock pump wires and low speed resistor pack are all in place otherwise.
Care also needs to be taken when installing it so it's got a solid seal to the outlet tube in the tank. If the o-ring isn't sitting or sealed right you could have pressure leaking back into the tank.
Dale
this is an issue. car will show symptoms, long crank time being one of them
I took this picture before installing the pump in the tank, to me it looked OK.
I didn't use any o-ring with this pump since I had to cut the metal tube and used this special fuel hose along with 2 clamps, that were coming in the walbro kit.
I also verified that the pump I've ordered is the HIGH PRESSURE walbro 255, (GSS342) and it is the case ! (Because, apparently, they also sell 255 in oem pressure...)
I've also read this on Racing Beat website, so I guess the hard rewire will help a lot in my case.
I'll make some tests and remove the pump soon so I'll know what's going on.
A lot of aftermarket pumps draw more power than stock. Even the oem pump can see voltage drop because of the insufficient gauge wiring mazda used in parts of the circuit. This is compounded by age and heat. We solve the issue with a relay kit and wiring upgrade. We don't like the 255s for anything but a very mildly modified car. We prefer the 450. I have a complete setup if you need. https://www.irperformance.com/product/irp-fuel-pump-adapter/ Put a volt meter on the pump wiring in back and see what its doing.
Ok, before I do the rewire fix, I wanted to check voltage with my current setting in order to see the improvement voltage after the fix.
So, I unplugged the harness plug on top of the pump cover, and I inserted 2 wires inbetween the male and female harness plug (this is the only way I found to attach my voltmeter while the pump is connected, if you've got better techniques, please let me know how).
I got 12,4V at my battery.
Engine off, I get 12V at the pump harness (pump disabled)
BUT, when the pump is turning (I'm using a jumper in the diagnostic box to activate the pump) , I get only 3,6V..
Is this normal when the engine is off ? Will it increase when the engine and alternator will turn ?
I expected a low voltage, say 8 or 9V, but not 3V...
So, I turned on the engine and the voltage at the pump was at 7,6V only. (Video attached) https://www.youtube.com/watch?v=cnpI...ature=youtu.be
This is low, (still , the afr is ok) and I'm pretty concerned that it stayed under 8V even until 6k rpm ... like if the fuel pump resistor was enabled all the time.
I was not driving the car on the road, but I was in neutral in my garage. And I don't know exactly under which circumstances the fuel pump resistor should be shortcutted.
I checked my fuel pump relay (speed), and it's OK. So, I assume the fuel pump resistor should be disabled when not at idle, but it doesn't seem it's the case right now.
I also checked the fuel pump resistor, and I get aprox. 0,6ohm, which is normal according to the FSM.
Anyway, I will now do the Dale Clark's fuel pump rewire and see if the voltage get better.
under 1psi the ecu turns on the relay, and this has power going through the resistor . over 1psi the ecu turns the relay off and you should get 12v at the pump.
if you unplug the fuel pump, you can do some testing of the circuit and find where the voltage drops are. you measure battery voltage, and then voltage at the pump, its it within about 0.5v, you're in good shape. if not you can measure the voltage at various places in the circuit.
for example my FC looses about 0.5v, the relay takes about 0.1v, and the ignition switch takes the rest. i rebuilt the switch, the FD its easy to bypass (i suggest this anyways, its less current going through the switch, so it should last longer)
the next test is to hook up the pump and do the same tests with the pump running, you will find the pump uses some power, how much power nobody really knows (stock FD pump is around 2v)
Thanks a lot j9fd3s for these explanations.
Since I was gentle on the gas pedal and the car was at 0kmh in my garage, I think the boost didn't reach 1psi. That may explain why the voltage was so low (7,6V).
Anyway, I did the Dale Clark circuit relay rewire, and I was happy to notice an effective gain :
Engine off, pump running : I had 3,6V before, now I get 4,1V.
Engine on, at idle, I was at 7,6V, now I'm at 8,6V.
At that point, I thought it was normal, since the resistor was enabled (In my garage, not driving)
So I get the car out, and... the voltage stayed at 8,6V while driving gentle, and even dropped at 7V under heavy loads (10psi)
Like the ECU (PFC) didn't turn on the fuel pump relay, which seems stuck in the resistor circuit...
I checked the fuel pump relay : I could clearly hear it engaging when I connect the coils to the battery, and checked the 2 other pins: they were very low ohms... so, this relay is totally OK for me.
Then, I short circuited this relay and, indeed, instantly the voltage at my pump raised to 10,1V (engine off) and 12,2V while running. (11,8V under heavy loads). https://www.youtube.com/watch?v=LEbq...ature=youtu.be
So, why the ECU doesn't enable the fuel pump relay when it should ? (my map sensor is OK, I monitor it with the pfc)
Maybe I could just bypass this relay ? But I guess I'll need a full remapping soon ?
Cause, while the voltage was OK, the car didn't behave well under heavy loads it was hesitating, boost sometime stucked at 5psi, little explosions from the exhaust...
I think you answered your own question. Somewhere in whatever you "short circuited" (assume you mean by-passed) is the problem. You just need to trace it down. It may be poor grounding, corroded wire, etc. You should be able to do this with an ohm meter.
I think I need to unmount the relay box in order to check the cables under.
or maybe just check continuity between the trigger wire at the relay box and at the ECU harness.
I'm gonna investigate there soon then !
thank you guys
Not sure if mentioned yet but have you inspected both sides of the white bulkhead connector on the pump holder. It is common for it to melt and cause issues.
Also, even though a new fuel filter, it could be clogged if you got some trashy gas. That very thing had me chasing my tail years ago when a fuel pump went out.
Good find on the Fuel Pump Speed relay. The ECU activates that by supplying switched ground on pin 1K. If your PowerFC is never grounding that pin, the fuel pump will never get full power. Bypassing the relay is one workaround, but may shorten the fuel pump life. Bypassing the Fuel Pump Speed relay may also result in too-high fuel pressure if the regulator can't bypass enough fuel at idle when the demand is low and the fuel pump is running at full blast.
Man, I'd be afraid those terminals would fall off the hanger pins. Are they soldered on there? Just slip on female connectors? I am not saying that is your big voltage drop, just that I wouldn't trust that connection personally.
Good find and luck getting your pump up to voltage/speed!
Man, I'd be afraid those terminals would fall off the hanger pins. Are they soldered on there? Just slip on female connectors? I am not saying that is your big voltage drop, just that I wouldn't trust that connection personally.
Yes, get yourself a proper bulkhead pass-through. And make sure all your wiring and heat shrink is fuel rated. It's a lot more expensive and harder to find so most DIY is not fuel rated
03-07-20, 11:19 AM
