Author Topic: Another hard warm start issue. 89 RMC, 360TBI  (Read 822 times)

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Offline swissprobe

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Another hard warm start issue. 89 RMC, 360TBI
« on: July 11, 2020, 10:29:52 am »
Just to get it out of the way, yes I did search intensely on the forum, but couldn't find anything that would help matters.
I have the issue, that my 89 TBI 360 LA Ramcharger starts immediately when its cold, on the first turn of the starter. If it's warm (even when it sat in the sun at 90F) it barely will start. On the first turn of the starter it seems to start and then falls back to cranking for about 5-10s until it hesitantly starts. Once it  runs all's fine again, normal idle and so on.
The starter turns very well and fast, also when hot.
The only thing I had, once in a while is, that it bogged a little when I tried to accelerate harder. If I then modulated the gas pedal I could get around it and it worked fine. Didn't happen often, though. I ran fresh gas and injector cleaner, now it's not noticeable anymore.
Gas mileage wise, I haven't calculated it, but it seems in the regular range. A 4.5hrs drive through the mountains used approx 2 index marks on the fuel gauge.

This is a list of what I did to the car the last two months:
   - Replaced all fuel lines (not the one in the tank, they look new and the stamp on the fuel pump lets me assume, that it's one from 2016, Bosch)
   - I checked the fuel pressure, perfectly fine in idle and also on higher rpm(no load)
Fuel pressure after time:
4min = 10psi
7min = 8psi
30min = 6psi
   - Timing has been checked
   - New harmonic balancer (verified TDC with marks)
   - Spark plugs are fine
   - Spark plug wires tested for resistance = good
   - Visual check of both injectors, spray a cone, though not very fine (what does one expect at such a low fuel pressure, so I deemed it ok. Especially as the fuel only pours on the throttle blades anyway)
   - Fresh oil, new oil pan, new oil pump
   - New Thermostat
   - Checked both temperature sensors, coolant and TB. Both within specification:
     Coolant sensor
     21C = 11.3 kOhm
     53C = 3.7 kOhm
     93C = 0.92 kOhm

     TB sensor
     21C = 8.8 kOhm
     53C = 2.7 kOhm
     93C = 0.73 kOhm
   - New PCV valve
   - New O2 Sensor (Bosch)
   - Measured timing chain play, like brand new
   - New battery
   
   
According to the PO the engine has been replaced about 10 years ago, but only 2000Mi. The story could be true, at least I found tags on the engine that state it had been rebuilt. When I had the oil pan of to replace the oil pump, the rear main bearing looked brand new.

I haven't done a compression check yet on the engine.

I have the impression, that the car is way to quiet, it only has the catalyst converter, no muffler. I figure that the exhaust valve on the passenger side doesn't work anymore, I fixed it in the open position. Didn't make a difference performance wise, but a least it sound like a V8 at idle. As the clamps for the cat a rusted badly, I would have to cut them off. I have the new clamps here, but no tool to cut off the bolts. May the cat is clogged? But that doesn't seem to have an impact on starting in my opinion.

I have no error code.

From my understanding the control module uses atmospheric pressure and coolant temperature to decide how much fuel it needs for a startup. As the coolant sensor seems to be ok I could only imagine the MAP sensor to be bad, besides the control module itself.
(I have some experience with EFI, had a Megasquirt on my car for 1.5 years which I installed and programmed myself)

On the throttle body there's a nipple for a heated air inlet, mine is plugged with a screw, doesn't look stock. I can't find a connection for it though. Manual P.707

It starts perfectly if I restart it within a minute after shutting it of.
It starts faster if I floor the gas pedal.
So I checked the O-rings of the injectors, one had a very little scuff mark, probably not even a cause for a leak. I replaced it anyway, didn't make any difference.

Any other suggestions I may could check? I have to sell the car unfortunately as soon as I have the new title in hand. Had planned to keep it for quite a while. I'd like to sort this out before selling, would be nice.

I found some information on the forum:
https://ramchargercentral.com/vehicle-help/hard-starting-after-warm-up/msg1860694/#msg1860694
But I can't / won't replace the starter as I have to sell it. And mine turns very well, same engine revs as cold. On top it starts faster if I floor the gas pedal, doesn't seem to be connected to the starter.
1989 Ramcharger
390 TBI
Unknown lift, should be 3"
33" Tires

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    Offline DODGEBOYS

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #1 on: July 13, 2020, 09:46:43 am »
    a clogged Cat with cause a NO start , if you searched you didnt find the main cause of 1988 to 1991 driveblity problems and that is the connectors at the back of the right valve cover
    put your truck info HERE
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    Offline abesKIA

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #2 on: July 13, 2020, 03:03:10 pm »
    Quote
    - I checked the fuel pressure, perfectly fine in idle and also on higher rpm(no load)
    Fuel pressure after time:
    4min = 10psi
    7min = 8psi
    30min = 6psi

    Isn't this very low for a TBI?

    Offline ToxicDoc

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #3 on: July 13, 2020, 03:07:25 pm »
    Isn't this very low for a TBI?

    Yes, very much so. I wonder if the pump is starting to fail as it warms up. He should consider the regulator, filter, and maybe leaking injectors or even computer failure as it warms.
    '85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

    Offline dodge82273

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #4 on: July 13, 2020, 03:55:31 pm »
    the po stated psi after time , so after 4 mins of what ? OFF time it drops to 10 psi ? or is that 4 mins of running time ?
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline modelcitizen

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #5 on: July 13, 2020, 04:11:20 pm »
    Took that to mean residual pressure after shutdown,those #s seem ok.

    Offline ToxicDoc

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #6 on: July 13, 2020, 04:37:52 pm »
    Took that to mean residual pressure after shutdown,those #s seem ok.

    That would be a different story then. If it's just bleed down pressure, then the next thing I'd consider is a bad Hall-effect sensor. It can be failing and won't throw codes.
    '85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

    Offline swissprobe

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #7 on: July 23, 2020, 08:22:59 am »
    Yes, the numbers for the fuel pressure are after shutdown. During running condition (in neutral, not driving) the pressure is stable on 100kpa (14.7psi).

    I drove it now a while and roughly 300Mi, it runs fine, no bogging or whatsoever.
    Just the warm starting still takes to long.

    If the starter is about to fail, even though it turns the engine really good but draws to much amps, that may affect the pcm? I found that here in the forum. May I try to connect jumper cables to another car, then there should be more amps available for the starting.

    I also connected the fuel pressure gauge to the supply line, if I then start to clamp the return line, the pressure shoots up, I stopped at 50psi (fuel hose rating).

    I basically tested the system according to the manual.

    For the injector leaks, I checked both O rings an replaced one, though I think the replaced one wasn't even leaking. I put a paper towel under the injectors when I turned the engine off, couldn't see any trace of dripping.
    1989 Ramcharger
    390 TBI
    Unknown lift, should be 3"
    33" Tires

    Offline dodge82273

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #8 on: July 23, 2020, 10:21:02 am »
    when its warm and you want to restart , try this , step all the way down on the gas pedal and hold it there , then crank it . does it start a little better ? if so look for a leaking o ring or throttle body , allowing raw fuel to drain into manifold when OFF , creating a "flooded" condition .  Yes depressing the pedal all the way while cranking tells the pcm you are clearing a flooded condition , and it does NOT supply more fuel , just air ... this leaking could also account for the pressure drop off when OFF
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline swissprobe

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #9 on: July 23, 2020, 09:32:56 pm »
    @dodge82273

    That's what I was thinking as well, why I checked the the O-rings of the injectors. I floor it always when starting warm, as I assumed/hoped that the PCM will shut off any additional fuel supply during start up. That also speaks for the fact, that if the car is restarted within 1 or 2 minutes, it starts fine. What I don't understand, as the fuel pressure drops relatively slow, how that little amount already shall have such a huge impact on an engine of this size.

    I never thought, that the throttle body itself could be the culprit as well. Any location I could easily check?

    1989 Ramcharger
    390 TBI
    Unknown lift, should be 3"
    33" Tires

    Offline dodge82273

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #10 on: July 24, 2020, 03:18:12 am »
    WHOA ....... you ALLWAYS floor it when starting warm ???? , and if it sits too long its hard starting ??? well thinkabout that ............ the fuel regulator / check valve slowly leaks off pressure ,( acceptable) You turn on the key , pressure back , you FLOOR it ( as YOU say ) the pcm shuts off ALL fuel to engines intake because you foot says to do that , engine don't start ......... NO fuel ...... IN that case , keep your foot under the seat , turn key .... what happens ?
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline Jeffy45

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #11 on: July 24, 2020, 05:44:13 am »
    a failing ISC will also cause a hard  or no start condition. Hold to floor truck starts
    1988 Ramcharger LE 150 318 TBI 727 non-lockup.                   
           " If a law is unjust, a man is not only right to disobey it,   
                    he is obligated to do so"                                                   
                                                                 - Thomas Jefferson

    Offline swissprobe

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #12 on: July 24, 2020, 03:06:24 pm »
    Yes, I do floor it when warm, because it starts faster. It takes approximately 10-15s without flooring, maybe 5-8s when I floor it and it starts "healthier".

    But if the leak is somewhere, where the fuel drips into the intake, it has a flooded condition, therefore the flooring when hot helps.
    It would also explain, why the car jumps to life when cold, richer = better (if not too much)
    1989 Ramcharger
    390 TBI
    Unknown lift, should be 3"
    33" Tires

    Offline dodge82273

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #13 on: July 24, 2020, 09:10:17 pm »
     5 secs seems pretty good to me ... liquid fuel is NOT the same as atomized fuel ... LOOK in the throttle body after it has sat for a while , open the butterflys , do you see WET fuel down there ?
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline swissprobe

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #14 on: August 7, 2020, 07:40:43 pm »
    Thanks for all the help.
    But due to the COVID situation I had to make the decision to sell the Ramcharger.


    I haven't found the solution to it's warm start problems.
    1989 Ramcharger
    390 TBI
    Unknown lift, should be 3"
    33" Tires

    Offline Jeffy45

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #15 on: August 7, 2020, 08:27:05 pm »
    Because of lack of work? Really getting sick of this fake covid bullshit
    1988 Ramcharger LE 150 318 TBI 727 non-lockup.                   
           " If a law is unjust, a man is not only right to disobey it,   
                    he is obligated to do so"                                                   
                                                                 - Thomas Jefferson

    Offline ToxicDoc

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #16 on: August 7, 2020, 09:47:59 pm »
    Because of lack of work? Really getting sick of this fake covid bullshit

    Call it what you want, but it's not fake. i got a bunch of dead 40 year olds to back me up
    '85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

    Offline Jeffy45

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #17 on: August 8, 2020, 04:11:55 am »
    I meant all the bullshit that surrounds it
    1988 Ramcharger LE 150 318 TBI 727 non-lockup.                   
           " If a law is unjust, a man is not only right to disobey it,   
                    he is obligated to do so"                                                   
                                                                 - Thomas Jefferson

    Offline dodge82273

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #18 on: August 8, 2020, 04:13:54 am »
    a tbi that starts with 5 seconds of crank , may not of had such a big problem ..
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline ToxicDoc

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    Re: Another hard warm start issue. 89 RMC, 360TBI
    « Reply #19 on: August 8, 2020, 11:28:45 am »
    I meant all the bullshit that surrounds it

    Gotcha
    '85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241