Page 1 of 2 12 LastLast
Results 1 to 10 of 11
  1. #1
    Join Date
    Mar 2005
    Location
    Northampton
    Posts
    1,241

    Cutting out in hot weather

    I’ve spent some time trying to work out what this problem is and I can’t spot it so I’m hoping a consensus can be reached here.

    The car cuts out in hot weather (over 25 degrees C) and it seems to be more of a problem when barely moving in slow traffic. It gives a few seconds notice of rough running then stops. Last time it did it I noticed that the volts had dropped below 10v at the same time. It sometimes restarts straight away, and if given ten minutes rest it’ll be ok for a while. I’ve got around this by keeping the revs up and being aware of situations where this isn’t happen. The radiator fan is set to come on reasonably early and I’ve fitted an over-ride switch for the fan to turn it on earlier in case of traffic jams but I’m not sure that is the issue. The fuel vaporising in the pipes was also suggested but giving it ten minutes rest wouldn’t be sufficient to cool the fuel.

    My suspicion is that it is electrical, and that when moving slowly build up of heat in the engine bay is causing some component an issue. The question is what ?

    It’s a 4.6 RV8 with an Omex ECU. The injectors have been replaced recently as have the rubber fuel pipes with no resolution.
    David (AKA Firestarter29)

    Lead, follow, or get out of the way.

  2. #2
    Join Date
    Jun 2004
    Location
    Northampton
    Posts
    2,061
    Hi David where are you taking it to experience temps of 25? I know you’re not averse to a drive out. Spain at the weekend?
    What ignition system have you got? Distributor type? Coil type? Also mechanical or electric fuel pump? If electric where is it situated? If it is fuel vaporisation letting the engine cool down for 10 minutes would probably be sufficient to overcome that temporarily. Hope the combined wisdom on here avoids a visit to NMS!
    Dek.

  3. #3
    Join Date
    Jan 2006
    Location
    Chelmsford Essex
    Posts
    1,756
    Your volts drop sounds like your issue.
    Fan draw is a high current draw and if your alternator is not keeping pace with all the consumption your ECU might not have enough voltage..
    Run the engine and monitor your ECU feed voltage. Switch on head lights fans and see if the voltage drops. This should eliminate or point to earth or alternator issues.
    Heat to the ECU might be eliminated . Try some heat shield as a temporary measure and see if this cures the issue .

  4. #4
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    43
    Posts
    4,981
    Quote Originally Posted by Firestarter29 View Post
    The car cuts out in hot weather (over 25 degrees C)
    Good news! It's not forecast to be warm again until 2022 (and is currently forecast to pee down on the 28th for our wedding)

    Anyway - as others have said, I'd start looking at the alternator if the system voltage is falling that far. That and all of the main battery feed joints, especially any near the engine bay, as a poor connection could heat up and cause a high voltage drop across it.
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  5. #5
    Join Date
    Aug 2014
    Location
    Lincoln UK
    Posts
    126
    Agree with other comments, suggest you focus on ECU supply voltage, then elect ign, then fuel supply. Most likely IMHO would be HV ign system, particularly if you have one common coil providing the spark energy. Such coils do have history of high temp related failures so if the ECU volts is ok then swap out the ign coil.
    Another wacky thought is ECU cooling. Components inside may get compromised with overheat and it could be impending failure or simply be the orientation of the ECU. If the cooling fins on the ECU (it’s heat sink fins) are horizontal the unit is not cooled as well compared with a vertical orientation. Surface heat is convected away easier when mounted this way. Unlikely I appreciate but something else to consider (like you need more variables!).
    Also, if you keep holidaying in Scotland then you probably wouldn’t have any further problems 😂😉🥶

  6. #6
    Join Date
    Apr 2011
    Location
    Bishop Auckland
    Posts
    326
    David, it could be heat soak from the engine causing the petrol in the carb to boil over - I used a phenolic spacer under the carb to insulate it. If you have fuel injection it won't be heat soak!

    James
    James G
    Purple Dax / Ford 260/4 speed toploader all in need of TLC and cash but the dreams are there. Dream on - car now blue, Ford 302 and Tremec T5, 6 years later....

  7. #7
    Join Date
    Mar 2005
    Location
    Northampton
    Posts
    1,241
    Gents, Thanks for the replies, I’m slightly heartened by the number of comments aimed at the ECU voltage / heat issues. Measuring the supply voltage as Jon suggested is where I’ll start, but doing this when / as it cuts out is trickier. I’m not sure it’s overheating as it is mounted inside the passenger footwell on the top surface - heat may be conducted there but there’s no hot air flowing over it. Still, it’s not a huge job to insulate it.

    Dek’s questions are always valid - except these are usually summer problems and unlikely to occur in an autumnal Northampton and Graham ought remember how warm it was in Scotland for the few days we were there, but don’t remember it being a problem then (maybe i was distracted by the malfunctioning clutch - now fixed) I did appreciate the comment about more variables may not be being helpful., However, back to Dek - It’s running coil packs, the fuel pump is electric and in the boot and the fuel lines are well away from the exhausts and are insulated in places where convection may be an issue.

    My gut feel is that (as Aaron suggests) it is some sort of dodgy connection which only appears in certain conditions of temperature (maybe after a few minutes build up) which would tie in with the voltage gauge suddenly dropping. Much of the engine wiring loom was replaced last year (well, the ECU loom at the same time as the injectors) which then suggests its something that has been on the car for a long time. Finding it will be the issue. I might consult an auto electrician…

    Thanks everyone for your suggestions, more suggestions would be welcome but I’m starting with ECU voltage, ECU insulation and dodgy connections on the larger engine wiring systems.

    Finally, Good luck for Aaron’s oft-postponed wedding !
    Last edited by Firestarter29; 22-10-21 at 07:28 AM.
    David (AKA Firestarter29)

    Lead, follow, or get out of the way.

  8. #8
    Join Date
    Jun 2014
    Location
    Swansea
    Age
    57
    Posts
    166
    Hi David

    You mention that the ECU is fitted in the footwell and no hot air is flowing over it. However, as BomberG mentioned the ECU would have cooling fins on it to help it cool down. In the footwell the heat generated by the ECU itself may be causing the issue as the heat may not be removed by cooler air blowing over it.

    As you say after a short time with the engine turned off the fault goes away. This could be because the ECU has had time to cool down as it is not generating its own heat while turn off.

    Just a thought and something else to consider.

    Regards

    Rob
    Rob

    AK Gen I - 4.6l Rover V8, Stage III heads, MC1 cam
    On the road March 2019

  9. #9
    Join Date
    Jun 2004
    Location
    Northampton
    Posts
    2,061
    Hi David
    Given what you’ve said now I too think fuel vaporisation is unlikely to be the culprit especially in autumnal Northampton. Can the coil packs be tested or are they cheap enough to replace? Presumably they could also malfunction with under bonnet heat.
    Dek

  10. #10
    Join Date
    Dec 2015
    Location
    Fairseat, Kent
    Age
    62
    Posts
    70
    My EFI car was suffering from intermittent stalling when pulling up in traffic. The water temp reading between 60/80C. My AIT was recording 70C + and so I heat wrapped the headers and down pipes to the collectors as well as moved the air filter with the MAF and AIT down lower in the engine bay with the filter protruding slightly out of the D/S inner wing. Net result is a high reading of 36C AIT and a much happier tick over when in traffic.
    I'm happy with the outcome albeit the fitting of the wrap was pretty nasty job.
    AK Gen 2 with LS1

    SE UKCC Area Rep

Page 1 of 2 12 LastLast

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •