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Old 07-25-2020, 11:51 AM
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Need a little help

I hope some of you FI guys can help me out here


The short version of the story is my truck sat for the better part of 3 months while being repainted. It was started and ran every week or two during this period but never run for long because the tank was very close to empty. It ran fine when parked but now that it is back together it starts when cold but as soon as it gets warm it starts having issues and will only stay running at about 2000 rpm. If I let off the gas it sputters and dies and is very difficult to keep running. This morning I warmed it up and made a data log at idle. It took numerous attempts just to get it to idle, you can see the restarts in the log, I let it run for a bit then gave it a little gas and let off and it sputtered and died, which is at the end of the log. Can anybody tell me what's going on and how to fix it?


Here are the details of my engine
Stock 1972 AMC 360, TH400 transmission, Fitech 39001 (2 barrel), a Fitech 40102 fuel pump mounted in the fuel tank, (not in a fuel command center), No timing control, No fan control


Here is a link to the log
https://1drv.ms/x/s!AtllmUWFvoeUhR5c...C__6Y?e=qqgcL7
Thank you in advance for any help
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Old 07-26-2020, 07:21 AM
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Can't open the log , but could be because that the fuel tank was almost empty that the carb is clogged with some residue from the bottom of the fuel tank!?

Or because the warming up is playing a part , maybe a intake leak below the carb or some gasket from the carb is letting air into it.
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Old 07-26-2020, 02:27 PM
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My first thought was the fuel filter clogged and I am about to go check that/


For those who might not be able to see the One Drive stuff here is a snip of it running badly



and another of it when it was running well



The differences I see are
Good / Bad

I (AFR TRIM) =a little higher. 11-12 is normal, in some it was as high as 40


K(IDLE FUEL L)=120 / 129.7


R(SPARK ADVANCE)=14 / 18 I'm not using timing control so shouldn't matter


U=13-15 / In this section it is in the low 30s but in other areas it's -7 to -9 (that's negative 7 to negative 9)


V(FUEL PUMP)=97 / 84 This varies normally from 80 to 100


X(AIR TEMP)= 96 / 68 I assume this is the air temp under the hood. when the 2nd one was taken the hood was open.


Y(CYLINDER TEMP)=154 / 132 This is some sort of wild guess on the fuel injectors part.


Z(BATTERY)=12 / 14 The before was with the under powered Motorola Alternator, after is Powermaster 150 amp.
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Old 07-26-2020, 04:13 PM
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Have you measured your voltage to the computer? Or grounds from the computer? I am wondering if some of those values are off because of bad/missing grounds or low reference voltage.
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Old 07-26-2020, 07:11 PM
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I haven't done anything yet, wound up having to do the weekly running around today instead of working on the truck.


I know the Fitechs are sensitive to interference from spark plug wires and I haven't shielded the wire but up to now there haven't been any issues so I haven't worried about it. I'm really hoping it's something simple like the fuel filter but it starts acting up right at the temperature it goes into self tuning mode so I'm afraid it's something computer or sensor related.
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Old 07-26-2020, 07:14 PM
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Start with basics...
Check fuel pressure
Check voltage @ fuel pump
Check + connections and grounds.
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Old 07-27-2020, 12:30 AM
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OK I pulled and cleaned the fuel filter, that wasn't the problem. There was a small amount of debris but not much.



So then I moved the spark plug wires as far away from the tach wire as possible. No help.


I checked connections, all of them seem good.


Fuel pressure is strange. when I initially turn the key on it is 58PSI as it should be but drops to 40 or so at idle, then if I rev it it drops more. because this system feeds fuel back to the tank I don't know if this is normal or not because I've only ever checked the fuel pressure prior to start and at idle, but it seems a bit low. I'm currently trying to figure out how to set the fuel pump back to initial setting to get full pressure all the time. I wonder if I should cap the return line and see what kind of pressure I have while running.


The popping through the throttle body is bothering me so my plan for tomorrow is to pull the plugs and check them and the compression, maybe new plugs as well. I like to change out the spark plugs ever year or two anyway.
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Old 07-27-2020, 10:49 AM
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Pressure should not drop.

If it is dropping either the pump or regulator isn't working properly.

The popping through throttle body is likely because it is running very lean.
Just looked @ AFR on bad running...it is WAAAAY too lean!!!
18.3 18.6 17.9
that's piston melting lean

https://lh3.googleusercontent.com/OJ...-no?authuser=0
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Old 07-27-2020, 05:32 PM
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Lean AFRs aren't terribly dangerous at idle, but they won't help it run well.

You're seeing lean AFRs despite increased fuel trim and consequently longer injector pulsewidth. That does suggest a fuel pressure problem.

I'd be very interested in seeing what fuel pressure is like when it runs well and when it runs poorly, as well as voltage at the pump (measured directly with a voltmeter) under those conditions. It's possible that either the fuel pump or the circuit that feeds it are working well when cool, but failing after a few minutes of work.
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Old 07-27-2020, 05:39 PM
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most fitech(s) i have seen run pretty rich@idle.
16/17/18 AFR won't run worth a crap and if his pressure falls with throttle it will never drive.
he'll just get lean backfires out throttle body and stalling.
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Old 07-27-2020, 05:42 PM
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Agreed. It's definitely not going to be happy idling that lean.

My limited experience is that most engines idle a little better just on the rich side of stoich.

Fuel pressure at the rail needs to be verified. This could be as simple as a dodgy pump or a poor connection that transmits less and less power to the pump when it gets hot.
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Old 07-27-2020, 06:27 PM
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even though i have 3 rigs with howell FI the only problem i had ever with running poorly and dying was a bad TPS, why do your readings indicate zero at idle - there should be something there IIRC is like 1 volt closed throttle and Wide open 5 volts more or less?

alot of guys here are experts on FI, i am only a humble beginner who installs pre-made kits

steve
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Old 07-27-2020, 06:58 PM
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tps in log is probably a %
modern systems tend to auto-zero
so 0=idle and anything above is a calculated % based on pcm/sensor reporting
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Old 07-27-2020, 08:39 PM
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thanks tony....wow thats new, ok so how can the tps voltage be above 6 volts? or is this FI a non GM based system?

steve
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Old 07-27-2020, 08:59 PM
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Wow, getting a lot of discussion and I'm learning a lot. Thank you everybody. Fitech tends to have less than stellar customer service and I don't know a lot about EFI so I have to rely on the generosity of others.


So there is a story about PWM and AFR. PWM is supposed to come pre set to 74.9 but for some reason mine came pre set to 80 but at the time I got the setup their website said 74.9 was for the frame mounted pump but to reset it to 40 if you are using the fuel command center. Since I am using the the same pump as the command center but in the tank I asked Fitech what I should set PWM to. They sent me 3 different emails about completely different things and FI systems and none about PWM. and they eventually just quit answering my emails rather than actually answer my questions or actually read my emails.


Driving it in the beginning it became apparent PWM at 80 was far too high and was causing some issues so working with some people we eventually worked it down to 66. It ran really good at that.



The preset fuel mixture was also far too rich and eventually I got that adjusted so it was 13.5-13.8 at idle and low to mid 14s at speed but it always had a tiny lean tip coming off idle but never long enough or severe enough to matter.



You can adjust the target mixture and I've always kept them a little on the rich side but never as rich as the factory settings.



Now one thing many people have run into is whatever it is that controls the fuel pump in the Fitech system has been known to fail and cause issues and people often have to go to some kind of fuel pressure regulator instead of the factory controller but I don't even know the first thing about setting something like that up but that kind of thing seems to be the direction this thread is heading. Hopefully someone can nelp me out if it comes to that.


I did set the PWM back to 80 and it helped make it run better. Fuel pressure at idle is only 35-37, which seems low and pressure rises when the throttle is moved instead of dropping. The pump is running at 99% all the time but there is still a severe lean spike, hesitation, popping back when I hit the throttle quickly. I think they have an adjustment to increase the fuel when you accelerate but I'll have to research that. I'm also considering the possibility of buying a frame mounted pump and or a fuel pressure regulator if I can figure out how to make such a thing work correctly.
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Old 07-27-2020, 09:32 PM
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I am NO fitech expert!

Pumps create fuel flow NOT pressure. PWM drops voltage to reduce the load and HEAT on a fuel pump. It should NOT drastically alter pressure.

The regulator sets the pressure and is referenced via manifold vacuum.
Normal EFI systems maintain a set pressure via the regulator.
Under load and heavy accel the pressure should rise and be rock steady.
They do this for several reasons but mainly for consistent fuel delivery.
An injector is rated to flow "x" amount of fuel @ this pressure.
When pressure drops, the expected amount of fuel the engine receives is no longer accurate.
The pcm is then operating in unknown territory and the programming is not able to compensate because that constant is not accurate.

It seems to me you have a fuel delivery issue. Something is no longer functioning correctly. Be it the circuit, the pump, the regulator, etc.
Is this a fitech fuel pump?

As an experiment maybe temporarily disable PWM or set it to 100?
See if it behaves better.
Also check to see what disconnecting the vacuum line @ regulator does to fuel pressure...it should increase.
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Old 07-27-2020, 10:06 PM
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Yes!! (What tony said)
Also, make sure you take good notes on what you have done. You do not want to make any changes, then forget about them, and have to troubleshoot them when you figure out your fuel delivery issues. I would put all settings back to where they were when it ran well and focus on your fuel pressure.

If you make a change and that does not fix the problem, put that setting back to where it was.
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Old 07-28-2020, 08:03 AM
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Alright, I know nothing about FiTech or about this particular system, so I'm doing a little reading here:

https://fitechefi.com/product/39001-...-400hp-system/

Evidently there is a regulator built into the system, preset to 43.5 psi. FiTech says it's an "OEM style" regulator. The location of the regulator and its OEM application were not clear, and i didn't find installation instructions for this kit, but it looks like it may be mounted inside the throttle body itself.

If the regulator is set to 43.5 psi, you should have that pressure at zero vacuum (WOT) and less at idle. As Tony said, the regulator's job is to maintain a constant difference between manifold pressure and fuel pressure. Since intake manifold pressure is lower than atmospheric (i.e. in what we call vacuum) at idle and cruise, fuel pressure is lowered by the same amount by the regulator. Fuel pressure should always be 43.5 psi higher than manifold pressure. If fuel pressure is not consistently 43.5 psi above manifold pressure, it's time to figure out why.

PWM settings are beyond my experience. The systems I have worked with all have fixed voltage going to the pump, with pressure controlled solely by the regulator.

It would be interesting to read the installation instructions.
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Old 07-28-2020, 09:34 AM
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Quote:
Originally Posted by babywag
I am NO fitech expert!

Pumps create fuel flow NOT pressure. PWM drops voltage to reduce the load and HEAT on a fuel pump. It should NOT drastically alter pressure.

The regulator sets the pressure and is referenced via manifold vacuum.
Normal EFI systems maintain a set pressure via the regulator.
Under load and heavy accel the pressure should rise and be rock steady.
They do this for several reasons but mainly for consistent fuel delivery.
An injector is rated to flow "x" amount of fuel @ this pressure.
When pressure drops, the expected amount of fuel the engine receives is no longer accurate.
The pcm is then operating in unknown territory and the programming is not able to compensate because that constant is not accurate.

It seems to me you have a fuel delivery issue. Something is no longer functioning correctly. Be it the circuit, the pump, the regulator, etc.
Is this a fitech fuel pump?

As an experiment maybe temporarily disable PWM or set it to 100?
See if it behaves better.
Also check to see what disconnecting the vacuum line @ regulator does to fuel pressure...it should increase.




It does seem like a fuel delivery issue but that is all handled by the fuel injector itself. I have no idea how to change that. Fitech has made a lot of changes to it's website in the past year and it now says the fuel regulator is set to 43.5. Today pre start fuel pressure is around that 43.5. which is weird because it used to be higher but that seems to be where they say it should be. After startup pressure drops to 38psi, then after revving a bit it settles to 34. Maybe running it so low on gas damaged the pump or maybe that is just because of the return line or maybe something else but that is what's happening today.



Yes the fuel pump is a Fitech fuel pump. It is essentially a replacement pump for the fuel command center but mounted in the fuel tank.


I'm considering buying an externally mounted pump and seeing how that works out but my buget is so far in the rear view mirror another $100-150 is a real stretch.



I have been making adjustments. They may just be work arounds but it seems to be running fairly right. No more popping or lean spike on acceleration, but there is a slight spike on deceleration.


I would post a new data log but for some reason the controller is no longer storing data logs. It acts like it is making them but when I plug it into the computer there is no log to be found. I'm waiting to hear from Fitech about that, hopefully it's just a software issue.
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Old 07-28-2020, 09:47 AM
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I would avoid making any more changes to the tune. It seems much more likely that you have a physical problem that needs to be corrected.

The regulator seems to be inside the throttle body assembly. Can you remove it to make sure everything is clean? I don't know if you have any means to test it by applying vacuum to see if it responds, but at least you can verify that it doesn't look gummed up and that it is sealing to the TB and getting a good vacuum signal.
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