fuel pressure, hard starting, has cured itself.... - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat
 
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post #1 of 14 (permalink) Old 11-08-2011, 01:19 PM Thread Starter
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fuel pressure, hard starting, has cured itself....

I've got a 2001 Intrepid using the 3.2, yeah, lucky me I know. It has been an awesome car for me from 60K to 215K now. I changed the timing belt and water pump both times at 105K and 210K and have loved working on this car.

Anyway, recently, long cranking times of 3-6 seconds seems to be the plague. I checked all the injectors for leaks and found none. IAC is clean, there are no engine codes. I did the fuel pressure bleed down test, and it went from 55 psi down to nothing in about 24 hours. It passed the 5 minute bleed down test the book calls for with no problem. I even removed the fuel pump relay and checked it for resistance on the control coil.

Now that I have hooked up the fuel pressure gage though, the starting issue has completely disappeared. At least for now. Is there such a thing as an intermittent fuel pressure problem in an otherwise mechanically sound vehicle? Battery is good, fuel pressure is good, injectors are good, there are no leaks, no hesitations at full throttle, idle is fine, just a hard start that seems to have cured itself temporarily I'm sure.

Any thoughts on where to proceed in tracking down the real problem? Fuel pumps aren't cheap if that doesn't need replaced yet. I am trying to find what is actually wrong as opposed to shotgunning, which is really easy to do and sort of expensive.
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post #2 of 14 (permalink) Old 11-09-2011, 12:24 AM Thread Starter
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more info now from a few tests

I got lucky and caught the engine on a bad start while I had the fuel gage plumbed into the rail. Also, I noticed that the fuel pump didn't make it's usual strong routine sound when it came on. It was weak, and the pressure only came up to about 10psi. So I switched the key off without trying to start and turned the key on again. This time the pump came on strong and I got 55-60 psi. I tried starting and it cranked long and hard and then ran a little rough until it burned off the extra gas in the intake from turning the key on twice.

So, my hard starting is probably due to low fuel pressure, but what is causing the pump to have good pressure sometimes and not others? Is the fuel pump relay a common failure part of the system? I wish I had a way to check the voltage that was present at the pump the time it came on weak, but it isn't a predictable fault yet. Any ideas?
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post #3 of 14 (permalink) Old 11-09-2011, 12:41 AM
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Sounds to me like you have a bad fuel pump, bad fuel regulator, or a clogged fuel filter, in that order of probability. I'd lean on a bad fuel pump, but you could try just swapping the relay with the one for the brights or something and see if the problem goes away.

The fuel pump going bad could be intermittent, as well as the regulator.
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post #4 of 14 (permalink) Old 11-09-2011, 09:36 AM
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if you've never used a fuel system cleaner in it, that might be worth a shot. i had a long crank issue last fall and a few treatments of lucas oil fixed it. if it works it would be cheaper than replacing the pump and/or regulator and/or filter.
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post #5 of 14 (permalink) Old 11-09-2011, 06:04 PM
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Here's my diagnosis: Classic for either one or more fuel injectors leaking, which puts raw gas into the cylinders of those leaking and empties the fuel rail when the car sits for a few hours - *OR* either the check valve in the fuel pump or the pressure regulator leaking back into the tank which empties the fuel rail but does not put raw fuel into any of the cylinders.

In either case, it won't start unless you cycle the key because the 1 second or so of fuel pump running when you first turn the key isn't enough to re-fill the rail and create pressure (because it's full of air). Cycling the key lets the pump run enough short bursts to re-fill the rail and start building pressure.

If the problem is leaking injector(s), when it does finally start (after cycling the key), you likely will smell raw gas out the exhaust (due to the one or more cylinders having partially filled with raw gas). If the problem is leaking fuel pump check valve or pressure regulator, when it finally does start (after cycling the key), you won't smell raw gas (because all cylinders will initially be partially or grossly starved for gas). In both cases, it will run rough for a few seconds until all the air has worked itself out of the rail thru the injectors.

Using a fuel system cleaner (Sea Foam or Techron) in the gas tank, *can* fix it if the problem was some dirt or residue in an injector, the check valve, or pressure regulator.

If that doesn't work, injectors may have to be replaced, or fuel pump/sending assembly may have to be replaced (the raw fuel smell or lack thereof at startup should give a clue as to which).

CDMCCUL - I don't see a clogged fuel filter problem here. Symptoms of that would be OK starting and running under light load, but bogging under light, moderate, or heavy accerelation/fuel demand (depending on how badly it was clogged).


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Last edited by peva; 11-09-2011 at 06:08 PM.
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post #6 of 14 (permalink) Old 11-09-2011, 06:07 PM
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Quote:
Originally Posted by peva View Post
CDMCCUL - I don't see a clogged fuel filter problem here. Symptoms of that would be OK starting and running under light load, but bogging under light, moderate, or heavy accerelation/fuel demand (depending on how badly it was clogged).
Yup, I agree. I was only thinking on the lines of a slow running pump - but that would have to be really clogged, and constant... but yes, would have driveability problems to boot.
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post #7 of 14 (permalink) Old 11-13-2011, 10:43 AM
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im having same issues with starting sometimes. might have to try the seafoam in the tank.
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post #8 of 14 (permalink) Old 11-22-2011, 09:31 PM Thread Starter
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Deeper into the rabbit hole we go...

All right, $200 dollars for a new fuel pump assembly later, and all the incredible misery that goes along with crawling under a jacked up Intrepid to take the tank off and replace said pump, and the darn car just gave me a really hard start like it always does after it was driven for half an hour and parked for an hour. So I am back to the drawing board on this problem and searching for answers again, only now I am highly irritated after all that work and my $200 fuel pump that didn't make a hill of beans difference.

Is there any other relay or switch between the fuel pump relay under the hood and the pump? I am grasping at straws here.

Does the ECM vary the injector pulse width to start based on some temperature signal?

How long should I leave fuel pressure on the rail to check for leaking injectors?

Anyway, obviously something is still wrong, and I will be hooking the fuel pressure gage back up to the rail as soon as I can go rent the kit from Autozone. I think I'll go ahead and order a new plenum gasket and throttle body gasket since it looks like I will be taking the plenum off again to access the injectors and fuel rail. This hard starting problem is really getting old, especially since I've chased it around and around now looking for a problem only to find virtually nothing...

Does the ECM ever need to be updated? Again, still grasping at straws here.. Something short of buying a new car a piece at a time would be nice, but what do I know. I'm just a dumb aircraft mechanic who tries to fix my cars occasionally. I'll happily test or try anything, but nothing has worked so far.
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post #9 of 14 (permalink) Old 11-23-2011, 12:51 AM
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There could be several things that would cause a hard start but with the drop in PSI on the fuel rail that you saw you've eliminated most of them. A bad sensor or ECM wouldn't cause that. Have you checked the resistance on the wires from under the hood to the pump? If you have a faulty connection or wire damage that could cause a voltage drop, which I think would translate into low PSI.


PS
Reading the voltage would be even better if someone knows what it's supposed to run. All the FSM says is 12 VDC.

I'm also assuming everything - filter, valves, etc, - were part of the new fuel pump module. You didn't transfer anything from the old to new module?

Last edited by D76G12; 11-23-2011 at 12:58 AM.
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post #10 of 14 (permalink) Old 11-23-2011, 09:30 AM Thread Starter
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Quote:
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Reading the voltage would be even better if someone knows what it's supposed to run. All the FSM says is 12 VDC.

I'm also assuming everything - filter, valves, etc, - were part of the new fuel pump module. You didn't transfer anything from the old to new module?
Voltage is battery voltage at the connector that goes through the floor of the back seat and then to the tank and pump, at least it is battery voltage whenever I check it. The ground wire is also a good connection. That's why I was asking if there was another relay or switch somewhere between the one I can easily swap with another under the hood, because I don't know if I am missing a piece of this puzzle.

The new "pump" is a goofy looking collapsible sliding deal that squashes into position. I don't fully understand why it was designed to have a flexible link like that between the pump and the mount at the top that holds the pressure regulator, perhaps because the tank is plastic and bounces around a little and they wanted to be able to scoop up fuel off the very bottom with a moving target. I don't know, but this flexible pipe arrangement has worked well for 217,000 miles so far.

I am going to check the fuel pressure a little differently this time. I suspect that the engine getting hot may have something to do with why I get different results on the leak down test as opposed to checking it dead cold. Unfortunately, all my leak down and pressure tests were with a cold engine, and yesterday the engine had a hard start after being hot and a slight cool down period, so I will be trying to reproduce that scenario and looking for problems.

Anyway, any other ideas for me, let me know.
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post #11 of 14 (permalink) Old 11-23-2011, 10:16 AM
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i reread your second post where you caught the problem. the only things i can think of is the pump couldn't pull the required amperage for full operation (wiring), the pump was defective (you replaced it), or the pump worked fine and something was leaking the fuel out before the pump could build pressure.

did you use any fuel system cleaner as suggested?
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post #12 of 14 (permalink) Old 11-23-2011, 11:44 AM Thread Starter
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i reread your second post where you caught the problem. the only things i can think of is the pump couldn't pull the required amperage for full operation (wiring), the pump was defective (you replaced it), or the pump worked fine and something was leaking the fuel out before the pump could build pressure.

did you use any fuel system cleaner as suggested?
As a licensed aircraft mechanic, I have never heard of the need to use fuel system cleaners like all the ones that are highly advertised and widely sold in automotive. Maybe that's exactly what my car needs, who knows. Part of me says those products aren't going to make a hoot in a hail storm of difference. It looks like it is just snake oil and expensively bottled isopropanol and kerosene and a few other solvents and mineral oil type things, which it is if you read the MSDS on Seafoam and all the other similar products.

On the other hand, if I put one bottle of this concoction in my fuel tank, and it starts up perfectly from now on, I will be amazed and sing the praises of these products like everyone else. My experience has been that all the perceived benefits are anecdotal and unmeasurable, and about what you would expect for putting a little IPA in your gas.

Anyway, it may come to the point I put Seafoam in my tank. Until then, I will continue to check the things that make sense that actually measure the physical facts about how the system is working or not working. All this is in hopes of finding the problem the old fashioned way that has worked for decades and still has some value on these newer, computer controlled cars. There is still a lot of good old fashioned physical mechanical and electrical substance to these cars even if they have a computer that is dealing in unseen electrons.

I will update here when I find out what the sum total of all the physical checks show the operating status of the systems to be. I'd love for this problem to disappear with a $10 bottle of IPA and mineral oil, but I am also a mechanic at heart. We'll see which one has the solution, maybe both, I don't know. LOL

At least I am not too sore today from all that rolling around under the car yesterday.
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post #13 of 14 (permalink) Old 11-23-2011, 12:01 PM
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I understand your concern about using a cheap bottle of snake oil - and I wouldn't recommend using a cheap bottle of red STP fuel system treatment - but a bottle of something high end would likely affect changes in varnish deposits.

I work in a boat shop, and boat engines are very susceptible to fuel contamination and stale fuel problems. We are certified Mercury and Yamaha dealers We recommend using Mercury Quickleen in a strong concentration for all carb and EFI issues before bringing the boat in for carb service. We have seen stark improvements of using Quickleen vs. Seafoam even.

The MSDS for Quickleen states the following contents:
Alkylphenol polyoxyl
alkylamine
CAS #: TR SECRET-AKPOL
% BY WGT: 15 - 20

N-Propylbenzene
CAS #: 103-65-1
% BY WGT: 1 TO 5

Benzene, 1,3,5-Trimethyl
CAS #: 108-67-8
% BY WGT: 1 TO 5

Xylene
CAS #: 1330-20-7
% BY WGT: 1 TO 5

Benzene, 1,23-trimethyl
CAS #: 526-73-8
% BY WGT: 1 TO 5

Mineral spirits
CAS #: 64742-47-8

1,2,4 Trimethylbenzene
CAS #: 95-63-6
% BY WGT: 5 TO 10

Cumene (skin)
CAS # 98-82-8

Again, I do not like "Mechanics in a Can" or "Snake Oil" - and even those that are good, when used improperly, do no good. In problem boats, we will run the concentration of Quickleen very strong, more along the lines of several ounces per gallon, as apposed to the recommended concentration of 1 once per 5 gallons. Quickleen retails for about $16 for a 12 ounce bottle, so it isn't cheap, but it isn't out of range either.
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post #14 of 14 (permalink) Old 12-16-2011, 11:59 AM Thread Starter
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And the solution is....

So, this has been a long time in coming, but the starting problems are gone completely. The car runs smoother, accelerates better, and gets less mileage now than I have ever seen before. The lower mpg is probably my fault and the cold weather, I am just thankful to have a car that runs right and starts perfectly every time.

I didn't buy any of that injector cleaner or fuel treatment, so it will remain a mystery if the solvents and mineral oils would have cured the problem. I will attempt to use those products in cleaning my old injectors and see if they are worth the extreme price.

What I ended up doing has something to do with the deal I found on amazon. They had remanufactured (whatever that means) fuel injectors including new O-rings for $6 apiece and I bought 6. I had previously bought just the O-ring kits from Autozone for about $4 a set, so that tells you what a rip off that was. I basically got clean and new looking and working injectors for almost free if you take out the price Autozone charges for O-rings. Anyway, that was the solution.

For whatever reason, the old injectors would only leak when hot after shutdown, so I never actually saw them leak or any evidence of leaks, I am assuming they leaked. Now that I have spent upwards of $250 on O-rings, fuel pump, and injectors, I am going to use the old pump (still good probably) to test and back flush the old injectors that have new O-rings and see what they were indeed doing.

If new injectors from Autozone wouldn't have been $80 apiece (yikes!), I would have tried them sooner. I see the remanufactured ones on Amazon are now $25, and new are $50 something, but I only paid $6.50 or some deal. Anyway, injectors was the problem on my car, I intend to test the old parts I replaced and report here later what the cleaning products are capable of.

As a side note, I don't know what the working life of an injector like this is or even the reasonable life of fuel pumps, but I was really wanting to know if they were bad or not, and not just for the money reasons. It interests me that something that small and cheap can last that long. More to come.......
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