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Hard starting issues still - air intrusion

Discussion in '6.9L IH & 7.3L IDI Diesels' started by StationWagonDave, May 10, 2020.

  1. StationWagonDave

    StationWagonDave Registered User

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    I'm still having issues starting cold with my truck. I was a bit surprised- it sits for about a week at a time and last weekend it started on the 2nd try. This morning it wasn't wanting to start (it was about 35 deg out). I went down again around mid day (temps in the 50s) and after opening the drain valve on the fuel filter was able to get it started. I did hear air gurgling when I unscrewed the valve.

    There's a line that was uncapped below the filter. After finally getting my hands on the diesel owner's manual, I now realize that someone changed out the OEM filter. I guess the original one had a screw on cap and some sort of drain line? When I got the truck it has an aftermarket style fuel filter with the petcock so that's what I replaced it with when I did the injector service.

    I capped off that line today. I'm wondering if that's one usually does if the truck doesn't the original style fuel filters? Is there anything else I should look at? 7.3 ID I capped line.jpg
     
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  2. gnathv

    gnathv Full Access Member

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    The filter with the petcock should be fine. When I had my idi I changed the original to that style, my o rings on original gave me problems. The line you capped off should just be the drain and is open on the other end. Have you unscrewed the filter to see how full it is after it has set awhile? You mention temperature, is it possible your glow plugs could be Part of the problem? How long does your wait to start light stay on? I would plug it in for an hour and see if it’s still hard to start.
     
  3. franklin2

    franklin2 Full Access Member

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    With air intrusion it will usually fire off normally for about 3 seconds and then stall out when the air hits the injector lines. Then it's crank crank crank, and after a lot of cranking, fire off. If it never hits a lick at all, I am wondering if you have other problems.
     
  4. StationWagonDave

    StationWagonDave Registered User

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    @gnathv - I haven't unscrewed the filter to see if its full - I will check that before I go to start it again. I replaced the glow plugs last October and haven't done much driving at all since then. I'll have to time the wait to start light. Unfortunately I haven't a place to plug it in. Something I didn't consider when I was looking for a diesel! :(

    @frankin2 - Once I opened the petcock drain, it did fire up for about that long, then died out again. After that it fired up on (I want to say) the second try and stayed running. I do know some of the cylinders have lower compression, #7 being the worst! You should have seen the injector when I took it out. Looked like it had been at the bottom of the Atlantic with the Titanic. I'm wondering if the PO skipped on maintenance or ran the engine while it was low on oil? Being my first diesel I'm still learning.
     
  5. franklin2

    franklin2 Full Access Member

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    So you can get it running with just a little trouble. I would spray all the fuel lines down with brake cleaner so they are all clean and dry . Run it for a few days and do a good inspection, looking for any dampness in the fuel lines, return lines, fittings, etc. Look on top of the fuel filter around the fuel heater for dampness also.
     
  6. StationWagonDave

    StationWagonDave Registered User

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    I will do that. Thanks for the tip. It did start on the second try this morning. The Wait To Start light stayed on for about 7 seconds each time.
     
  7. franklin2

    franklin2 Full Access Member

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    Hmmm... that might be a little short. What type of glowplugs do you have in it? It was a little cool in Colorado this morning wasn't it? What does your wiring connectors to the glowplugs look like? Do they still have the white plastic pieces on them or has that all crumbled away?
     
  8. StationWagonDave

    StationWagonDave Registered User

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    I put in the Motorcraft ZD9 glowplugs. The wiring connectors are original and crusty. Some of the white plastic has flaked off. I was reading a thread on this site that mentions a handmade replacement that looked very well done.

    It had been starting fairly easily this last week (usually in two tries). But then on Friday I ran down to the park n ride (about 10 mins) and left it for the day. When I came back in the afternoon it wouldn't start. I let it sit overnight. It took 9 times to start in the morning. It wasn't cold; in the 60s. When I first started cranking no white smoke. I opened the petcock valve on the fuel filter and had diesel draining out. The schrader valve on my truck actually has a weird screw on cap which I haven't seen described on these trucks. Finally on the last try it fired right up no problems!

    I took it for a long drive at highway speeds on Saturday. I think it was DaveBen that said these trucks don't do well as grocery getters; I'm guilty of using my truck for this.
     
    Last edited: May 17, 2020
  9. franklin2

    franklin2 Full Access Member

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    It should sit there indefinitely and then start right up. That is how I use mine, just to haul trash and then the occasional trailer tow.

    I wonder if you have two problems at once. Some air intrusion and the glowplugs are short cycling. If you want to try something with the plugs, go out and unplug and plug back in each glowplug connector. Then go in and try to start the truck, and see how long the glowplugs cycle. If they are cycling longer, you have the same problem I had, the connectors get a small amount of corrosion and don't make a good connection. If this works, it will last a couple of weeks and then start doing it again.

    What I did with mine when this happened, I converted to a manual button. It always started after I did that, though sometimes it would run a little rough after it started, I believe that was a glowplug or two that had a loose or corroded connector and didn't heat very well. With the automatic controller, it will refuse to work correctly with a problem like that. With the manual button, it works anyways. I have started my engine with the manual button and 3 bad glowplugs, and it started right up, ran really rough, and then clears up. But it started, it was in the winter when I was plowing snow in a bad storm, I don't have time to fiddle with a finicky glowplug controller, I need the engine to start and run.
     
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  10. StationWagonDave

    StationWagonDave Registered User

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    @franklin2 - Do you think it would help if I replaced the glowplug harness? The one in there is original and kind of ratty. Also, there is what appears to be an aftermarket button on the dash. I haven't figured out what its purpose is yet; but I do know the truck still has the glowplug controller installed and wired up. My mechanic friend thought a PO may have had it hooked up to squirt ether into the intake?
     
  11. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Have you tried pushing it yet? It could be a manual control for the glow plugs. IIRC, all you have to do with the 7.3 style controller is to put a ground (not power) through your push button and hook that to the white wire on the controller to activate them manually. It's also possible that it was used for something in the past and has been unhooked.
     
  12. Philip1

    Philip1 Full Access Member

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    If you decide to replace the glow plug harness, you can either buy one from wes at classicdieseldesigns.com or build your own. If you build your own, you can use bullet connectors and 4mm (or 3.5mm for a tighter fit) silicone vacuum hose as a band to hold the connector to the glowplugs.
     
  13. franklin2

    franklin2 Full Access Member

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    I agree, try the pushbutton with the key in run. If it's hooked to the controller, you will hear a thunk under the hood and your voltmeter will drop to the left of the gauge.
     
  14. aggiediesel01

    aggiediesel01 Full Access Member

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    The way you describe the situation with your fuel filter I would be leaning toward a weak lift pump as a possible contributor to your problem as well. You may want to put a fuel pressure gauge on the shrader valve and see what it is while it idling and at 2500 RPM to make sure delivery is ok. IIRC 3-5 psi is the preferred pressure here. Pressure should start at 0 before cranking but come up quickly to keep the Injector pump fed. If your lift pump has a leaky check valve it could be letting fuel draw back and suck air into the top of the filter header from the return side. Another easy check for air is to put clear tubing from the filter header to first injector to see if air develops after shut down.

    The first place to start replacing wires on the brick nose truck GP system is the main GP feed wires that run through the engine harness connector. By now its typical that this connection is too corroded and overheated to delivery the current necessary for the GP system. Go get a 4 AWG starter cable about 6' long and run it from the main power connection on the GP relay to the hot side of your starter relay (on the fender). That will get a reliable source of current to the GP system. When you do this, make sure to remove the existing wires feeding the GP system from the hot side of the Starter relay and from the GP Relay. IF this experiment makes a significant difference in starting the truck then be sure to go back and add 2 parallel 6" lengths of 14awg fusible link wire to the feeding end of your new GP power feed or find a big enough fuse that will handle the current draw. If the new GP feed doesn't improve starting and you've confirmed good fuel supply and no leaks then double check for burned out glow plugs and a bad controller.
     
    Last edited: May 22, 2020
  15. StationWagonDave

    StationWagonDave Registered User

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    @IDIBRONCO and franklin2- So I went down and hit that button. Yup, its connected to the glowplug controller. When I hit it, i heard a "thunk" (click) and the voltmeter started twitching. It started after 5 tries. So I'm wondering if I did this in the correct order. I waited for the WTS light to go out and then pushed the button in for about 8-10 seconds. Is that right or should I be pressing it when the WTS is still illuminated? Also from what I read here my understanding of the manual glowplug switch is that the operator times holding the switch without using the WTS light. It seems like this may be an auxiliary switch that boosts the glowplugs? Or am I not understanding how it works?

    @Phillip1 - I would probably go with the pre-made set.

    @aggiediesel01 - The lift pump was changed out last spring by my mechanic. So I don't think it would be bad. I'll have to get a fuel pressure gauge. I do have a new controller; I should probably put that in.
     

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