user 84948

I'm trying to figure out where to hook up a fuel pressure gauge on my 2001 Civic. Can anyone help me out?

Thanks.

ezone

To measure pressure while running the engine, you'd have to use adapters to "T" a gauge between plastic line and steel line.

Or connect a simple gauge and hose to a steel line to measure regulated pressure without running the engine.


I might use scan data during a test drive to determine if there is a need for a fuel pressure test.
Pump problems are pretty rare. What's the issue?

user 84948

Here is the issue I'm facing: https://www.civicforums.com/forums/3...-like-gas.html

kamesen

Mr. Ezone,

What kind of scan data would you look at to determine if there is a need to monitor fuel pressure more closely? I've got an ODB reader that outputs data real-time.

In addition, I've tried to tee into the fuel pressure between the metal barb from the fuel rail and the quick disconnect fuel line but have been unable to find the proper adapter/coupling. Can you point me in the right direction? Any help is appreciated. Thank you so much.

-K

PS. In my case I suspect poor fuel pressure due to OE filter issues, and have found the DIY instructable from here on replacing it, but wanted to be sure before committing to the project.

ezone

I'd watch the primary O2 sensor voltage during a WOT acceleration run through first and second gears, maybe through 3rd gear if there's a clear highway to do it on.

If sensor voltage stays high then you aren't starving for fuel at maximum demand.

If sensor voltage drops low then you may have a 'lack of fuel' issue that would warrant a fuel pressure and flow test.


WOT means wide open throttle. MAXimum acceleration. Foot flat on the floor. Toes in the radiator. Let the trans shift at redline.

kamesen

Thank you very much. Will the Short/Long term fuel % trim numbers be of any use during the WOT exercise? If the STFT goes high in the + range during WOT, would that indicate engine overcompensating for running too lean condition?

Will post back with some results. Thanks again Mr. Ezone!

ezone

Nope.


If your scanner can put sensor info into a graph during a test drive and store it for later review, that may be handy as you can concentrate on driving.

Graph out TPS, RPM, and primary O2 sensor voltage.

kamesen

Mr. Ezone,

Please see attached for the results of the test. It doesn't seem like the voltage drops significantly... But I'm no expert. I will give more details shortly.

Run #1:



Run #2:

ezone

Looks like O2v stayed high throughout the duration of the WOT run. Looks like fuel delivery into the engine isn't an issue.

That can't rule out smells and leaks though.

All it says is the pump unit has the ability to deliver all the fuel the engine needs during maximum demand right now.

HTH

kamesen

That does help very much, thank you for your time.

Sit-rep:

Purchased 05 Civic EX about 8k miles ago at 150k. Amazing car. I started getting misfires in 1 through 4, with P0300 (random misfires) in the mix. I started diagnosing weeks ago. I did all the simple solutions (seafoam in the tank, checked gap on spark plugs, no carbon trails, no fouling, no fluids, confirmed injectors were actuating). Compression test showed all values within 10%. I did a test drive with EGR valve unplugged and it made a significant improvement. I finally settled on constricted EGR passageways even though I didn't have the EGR error code.

I got to the intake manifold, cleaned up the passageways and that made the problem go away, or so I thought. Even though the issue is mostly gone, every 1 of 20 starts misfires will occur upon ignition and intermittently throughout the drive. Misfires during acceleration, but also pronounced with low load on the engine while cruising at 50mph and low RPM. If I WOT in this condition, the CEL will flash intermittently. The misfires at low load led me to believe it was related to flow issues at the pump flowrate, thus wanting to measure fuel pressure, etc. Cranking the engine for a second longer after ignition starts seems to lower the probability of misfires during that initial idle, not sure if related.

Your input has made me consider the actual EGR valve, and how I haven't inspected or cleaned that yet. That's where I'll go next.

Thank you for any input you may have.

ezone

HOLD ON a minute, I just now realized your O2 graph says "bank 1, sensor #2" instead of sensor #1. Disregard everything and rerun the test using sensor 1.


I think it will still be OK but I'd like to see the front sensor data first.



Was at lunch during previous reply, was not reading closely...Sorry.

kamesen

No apologies required.

This tool gives the option to record up to four O2 sensor voltages from Bank 1 (even though I don't think there's that many sensors). When I initially added O2 voltage, Bank 1, Sensor 1, it did not record any data. For this reason, I think this may correspond to the primary O2 sensor, but I may be mistaken.

I will rerun the test with O2 voltage, Bank 1, sensor 1-4 data plotted just for thoroughness.

Thanks again.

ezone

I hope you meant intake manifold not exhaust. Carbon can build up in the intake ports along with the inside of the EGR distribution plate.

If you think it could be EGR valve, check EGR position sensor voltage in the data (if possible), see that it is below 1.25v at rest and it returns to the same voltage after each use....If its resting voltage changes that could indicate it may be intermittently sticking open ever so slightly, which can cause running problems at idle and especially cold.


Cold start misses, could be coolant entering a cylinder overnight. COuld be other things too.

WOT misses,,,,,,,, is it always the same cylinder setting a code at that time? (check fault code immediately when it acts up)

ezone

Noticed this thread was originally about an earlier car than yours, now that you posted YOUR cars info.

Graph bank 1, sensors 1 and 2.

A 2005 does not use a regular O2 sensor in the primary position, it's an AF sensor and its output is very different from a regular O2 sensor.
Now I wonder what your scanner is trying to display its value in...volts or milliamps.

May as well add STFT and LTFT to the mix, what the hell.

ezone

I'd be looking at MAP voltage too. If EGR sticks open at idle the MAPv usually increases, and fuel trims drop accordingly.

MAP voltage is usually below .90v at hot idle, no loads, neutral or park. If it's higher there may be something going on.

ezone

Sorry man, I'm all over the place (scatterbrained) AND trying to do a V6 ring job at the same time.

kamesen

Affirmative, intake manifold not exhaust.

It looks like the scanner defaulted to O2 sensor readings in Volts for Sensor 2, and mA for Sensor 1. Here is a test redo:



I'm unable to read/record EGR position sensor voltage in real time through this scanner. But I could take measurements straight from the harness at idle... Will try to observe any patterns from this.

This would be accompanied by white smoke from the exhaust upon ignition from a cold start, correct? Have not witnessed it.

Looks like MAP data defaults to inHG units output (what a PiTA). I'll check the Haynes to see what the spec values should be. I'll probably graph a cold start data with RPM, MAP, O2 voltage, and (?) and see what it looks like. I can only plot 4 variables at a time in one graph.

It hasn't happened enough to make a meaningful observation. I do check immediately after misses but like I mentioned, I'll go 19/20 commutes without noticeable misfires at all.


Thank you very much for your time, will report back accordingly (EGR cleaning will happen in the mean time).

ezone

Still looks ok to me.
I'm pretty sure you would notice if power dropped off during a wide open pull too.




Not a real common issue, but once in a while it happens.
It was just a thought.



Not on a cold engine, and not when there's only a trace.

There has to be heat and a lot of water (antifreeze) in order to make visible steam, a cold engine and a missing cylinder with a washed spark plug won't have enough heat.

All it takes is enough water to get the plug wet, that kills spark until the engine has run long enough to get the plug dry enough to fire. Dead cylinder miss might be anywhere from a few seconds to a minute, depending on how much liquid collected in the cylinder. If there was enough liquid it could hydrolock too, but you'd have far more noticeable symptoms long before that would happen.

I can select various data display values/units on my scanner. I'm just used to seeing MAP reading in volts, it's natural to me now.


Interesting. So it's almost random or something.
Are the other issues fairly random too?


Ever lost your gas cap or left it off.....and it rained?
Does your local gas station ever get water in their underground tanks?

kamesen

Interesting thought about the moisture in the fuel from the gas station...

Over the week I took off the EGR and cleaned it and reinstalled. Took it for a test drive and everything was still good. Finally today I noticed some hesitation again (after a week of commuting with no hesitation). My gas tank level was particularly low, but not to the red E marker yet and I wanted to test if somehow the misfires were related to low gas level. On the way to the gas station going up a hill it struggled and the CEL blinked on and off but disappeared after the hill. After filling up and driving around a bit more the computer confirmed P0302. It seems misfires are unrelated to gas tank level.

In addition, now that it indicated P0302, I can confirm this is the cylinder that almost always acts up first before potentially also giving P0300, after I did the EGR passage ways cleaning. Here is the freeze frame data for P0302:



The last line not shown is Absolute Throttle Position 23.3%.

Do I start all over again checking spark, gap, coil, injector, etc etc? I suppose I could check injector health with electronic measurements but I didn't think that would be the cause since it has also given P0300 previously. Thanks.

Edit: typos

ezone

Misfire set while driving...... was it at a somewhat steady speed?
(23% throttle and 32 MPH doesn't seem like it would be rapid acceleration)

Unplug (disable) the EGR valve and drive it. Will it still set another misfire code like you just posted, while EGR is disabled?

Quick and dirty would be swap #2 injector with one from another cylinder.
Then drive up the hill again (or whatever you did) and see if the misfire moved to the cylinder you put that injector in.

I like swapping stuff between cylinders to see if the code will follow a part being moved. It's just some work, no parts needed until you figure out what's causing it.

Example: if #2 has the code P0302
Swap plugs 1 and 2
swap coils 2 and 3
swap injectors 2 and 4
(write everything down so you don't forget where all the parts went)
Then see where the misfire shows up next.

Also....make sure you got the correct cylinder for #2. A lot of posters don't get the cylinders numbered correctly.

kamesen

Yes, we were cruising on a flat street a few minutes after having started the car when the misfires first became noticeable. It became exceedingly prominent when we started going up the hill... Yesterday when I re-installed the EGR and test drove, I couldn't appreciate any hesitation. Last week while commuting, no hesitation.

I will unplug the EGR and feel for misfires, and do a parts swap like you suggest. Thanks ezone!

kamesen

UPDATE:

I ended up swapping components as Mr. eZone recommended. Coil/ spark plug to other cylinders, and injector remained in cylinder #2 where it was originally. Surprisingly, after 6 months I haven't felt a single misfire.

In my field of work sometimes we see issues where tolerance build up causes system failure even though no single component may be failing on it's own. While my instinct points towards the injector (last component in the fuel system I didn't check), poor performance from the injector itself wasn't enough to cause misfires when coil pack and spark plug were replaced with the ones from other cylinders. As suggested, I made sure to write down which components went where in case misfires ever come back.

I just wanted to make it a point to come back in here and thank you personally, ezone. I've kept this thread open for 6 months to post the next troubleshooting update and ask for the next suggestion, but I never had the chance. Please send me a PM with an email address so I can buy you a beer. Thanks for the help you provided me and ALL you do for this community.

Sincerely,

-k

ezone

Thanks for the kind words!
Beers are appreciated but not necessary
Glad it's working for ya!

kamesen

PM me a place to paypal you sir! Cheers