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Forget the title; it's just what I think. I'd like to know what YOU think.
After a replacement of a valve cover gasket, the truck ran roughly. After a short test drive, it died at idle. I could start it and get it to run with the throttle open, but it would not idle.
I found that the fuel pressure was high, and the FPR would not hold a vacuum, so I replaced the FPR. That slightly improved matters, but it idles too roughly at idle to keep running.
Fuel pressure is at spec. with engine off, and will appropriately reduce with a vacuum pump on the vacuum input to FPR. The vacuum line is clear back to the "gas filter" on the plenum. The plugs were "sooty" but not wet, suggesting over-rich. There is a fuel smell near the exhaust when it dies. Compression is 175lbs +/- 6lbs. Leak down is w/I 10% on all cylinders, so I don't think I have a bad cylinder or valves. Ignition timing is spot on. (10° BTDC w/jumper). The CSI does not leak any fuel with the rail pressurized. (disconnecting electrical connector makes no difference).
I tried running the pump with the plugs out for 2 minutes, then cranking the engine with paper towels loosely at each plug. No paper towel was "wetted" by fuel blowing out of a cylinder.
When I shut off the pump, the fuel pressure will drop to 20psi in 120 seconds (the manual says it should be 21psi or higher at 5 minutes. ) If the engine is idling (poorly), when I shut off the pump it will idle much better for about 40 seconds as the fuel pressure drops to zero. A few seconds after fuel pressure reaches zero the engine stalls.
The sooty plugs and fuel smell, coupled with the dropping fuel pressure with pump off, and especially the better running with pump off, lead me to think I have a leaky injector. It makes the mixture over-rich, which prevents idling, but allows open throttle (rough) running. But I could be blind to something else.
A direct check of the injectors is not easy; I believe I need to remove the plenum, fuel rail and lower intake manifold, then reassemble the fuel rain to the (loose) manifold to pressurize the injectors. A lot of work if I'm "barking up the wrong tree."
[to do these tests, I removed the COR and the starter relay. I can run the fuel pump with the FP-B+ jumper, and I can run the starter with a jumper to the starter relay socket. So I can crank the engine with the pump off (to set timing), or run the pump without cranking the engine (to check for leaks).]
So things were running good to you changed a valve cover gasket ??
My first thought is what did you do ?? or not do??
Poor ECU ground can cause interesting things .
Spark plug wires mixed up if you wrench enough we all do it
Vacuum lines missed one got one on wrong ??
If the fuel problem was not present already changing the valve cover gasket did not make it manifest .
Unless the universe is out to get you !!!
Some fuel related things to think about
How old are your injectors ??
Ethanol does tend to cause rust in the steel lines past the filter on the engine side Rust causing strange spray patterns and failure to close completely .
Fuel pump having a internal leak will cause the pressure to drop
How does it start most times leaking injectors cause a long crank time.
I'm sure no expert scope, but I would have to concur with what Wyoming stated above, that sounds like a great solid list on where to start.
In your post you mentioned replacing a valve cover gasket not gaskets, did you do just the drivers side or both? At least if you only did one side it narrows down the possibility of what was removed therefore narrowing down what you have to look at if something went amiss during reassembly.
Pretty sure with the fuel injectors the first step is to ohm them and see if they are in spec. I want to say somewhere between 13 & 14 ohms. Yes, unfortunately the upper intake will need to be removed to get at them and hopefully the injector connectors don't crumble when trying to remove them.
I have the upper removed from my rig right now because of some seriously messed up camshaft wear so I decided to check the injectors for the heck of it and they speced out but I noticed when I was checking them that my readings started high, approx. 20 ohms or so and took a good while to settle down into the correct range. I'm not sure if that is normal or not. Think I am going to replace them anyways (245000 miles) while I I have everything apart.
Wish I had more to offer & hope you get it figured out soon.
... Pretty sure with the fuel injectors the first step is to ohm them and see if they are in spec. I want to say somewhere between 13 & 14 ohms. Yes, unfortunately the upper intake will need to be removed to get at them and hopefully the injector connectors don't crumble when trying to remove them. ...
The ohm spec is 13.4–14.2 Ω http://web.archive.org/web/201311071...90injector.pdf But if it was out of spec (e.g., open or shorted) that would only mean the injector wouldn't operate, and presumably would be stuck closed. I should have symptoms of over-lean then, not over-rich.
I've re-checked the plug-wire routing, and tested each wire with the timing light so I know (?) that each plug is firing.
I'm more than a little mystified by how well it idles for the 30-40 seconds after fuel pump-off. That could be explained by a leaky CSI (supplying fuel to all cylinders), but I can (and did) check that. If I had one leaky injector why would all the cylinders seem to run on?
Double check the grounds as said above. It really can cause some crazy issues that you can spend months chasing. It seems strange that the injector would just start sticking open like that at the exact time you did your valve covers.
I use a vise and I have a connector from a junk harness that helps me do it by myself. I dont know the exact pressure I am applying but I would say it is quite a bit. Also I run the hose from the syringe and make cleaner flow the oppisite direction in the injector. I found this test on a Youtube or Google search somewhere and so far it works for me. I am missing the rubber hose in the picture but it is to adapt from the syringe to both ends of the injector.
I only apply power for 1-2 seconds at a time when I flush and test to see if the injector is working, You know electric better then I do but applying power for longer then that, I would not think it would hurt the injector. For your test, you dont really need the power of the battery. A cheap tool that might help you determine if you have a leaky injector.
You also mentioned that it could be other issues. I wonder if your EGR could be stuck open causing some of the soot? I have solved a lot of problems on trucks by tearing the Intake down and cleaning all of the carbon out, getting the EGR operational as it will get clogged full of carbon and not operate, do a complete tune up with OEM parts, adjust valves and set timing per manual. I refer to it myself as Clean, OEM parts, and Timing. Also while you have the Intake off, clean all of your other sensors, especially the ones that are in contact with the cooling system. I have fixed many trucks that way.
I am just trying to think of what would cause a rich running or soot causing issue.
It looks like you and I have the same test set up. I used this a while back when I replaced a head gasket, and all the injector seals and connectors.
I held the syringe in my fist and pressed down on the plunger. I didn't do a measured test, but I don't think I can push my thumb down with more than 5 lbs-force, and the diameter of the syringe is large enough that I don't think I got more than 5-8psi on the injector. (instead of ~40psi) As a result, I got a thin stream of fluid (paint thinner) rather than a full spray. I was happy with it for testing that the injector cycled, and it was an easy way to push paint thinner through the injector, in both directions.
I don't think this setup would show if my injector is leaking now. When I switch off the pump, the pressure drops quickly from around 40psi to just below 20psi, where it sits for quite a while. If that test is showing a leaking injector, it looks like the leak stops at around 20psi. So my hand-powered injector tester wouldn't show the leak.
Well, I guess my diagnostic skills aren't as good as I hoped.
To test whether I had a leaky injector, I did not want to remove the fuel rail (where would that get me anyway?), or the intake manifold. So I decided to remove only the plenum (upper intake manifold). Then I put 1"x11" strips of paper down each intake port, so the end of the paper was under the injector (I should probably have used "blotter" paper, but I have no idea where I would find that anymore). I hooked up a bypass for the fuel return, and using the jumper ran the fuel pump for 60 seconds.
The strips of paper came out completely dry; I'm now confident the injectors are NOT leaking. After pressurizing the system for 60 seconds, it took 3 minutes for the pressure to drop to 21 psi (the spec is 5 minutes; since I now know my injectors aren't leaking, that's all due to a 23-yr old weak check valve in the fuel pump).
But, like all of us, I just needed to "widen my gaze." With the plenum off, I could see that I had pulled the wires from the connector to the #1 injector. Probably while wrestling the plenum back on after working on the valve cover gaskets. I did replace all 6 connectors not-too-long ago; it seems clear I didn't do a good enough job crimping the connectors for #1 The good news is that my set of new connectors came with 3 pins for each connector, so I had 6 left over (and like others here, I save almost everything that could have use some day). Plus, I'm getting pretty good at getting pins out of connectors. (yes, I also did a modest pull-test on the other 5 connectors.)
For those who wonder, to check fuel pressure (the easiest way) you need to install a schraeder connector.
I left it "permanently" installed. You can sometimes get this connector separately, but I got mine with this set: https://www.amazon.com/Actron-CP7838...UKC/ref=sr_1_1
Alas, I just can't explain why my symptoms looked so much like too-rich, when the problem was actually no fuel to #1. A head-scratcher.
there are other options for installing a fuel pressure gauge, including a permanent installation. the union bolt at the CSI is replaced with a fitting that allows a gauge to be hard-mounted (i'd only use a liquid-filled gauge).
At least you found the problem scope!!! What type of crimper did you use when you replaced them prior? I remember buying a specific one from Ballenger motorsports when I did mine a number of yrs back. I had a tech write up in the tech section when I did mine but the pictures are now dead.
07-19-2016, 10:09 PM
How old are your injectors ??
