Dead engine on hot idle - help, advice, suggestions sought !
Discussion
New 4.6 with ex 4.5 reworked heads. EFI on Megasquirt, torque cam not especially lumpy.
No problems when driven for less than 30 minutes, seems to need a really good warm through before the issue appears, also only when cooling fan running (only have 1 at the moment) and coolant at 90 degrees.
Symptoms are when changing down or coming to a halt (so revs below 2000, clutch depressed) the engine dies, no stutter just stops. If speed high enough will allow jump starting although revs then need to be kept at 1500 plus or will stall again.
Sitting at idle in the garage everything will be fine, 900 rpm fairly even, 14.5 - 15 AFR, cooling fan on constantly but holding 90. No warning will suddenly die. Will start immediately but needs 1500 held or dies again. After a a short while will idle ok again.
Initially I thought maybe the coil as it does get hot, however it is brand new. This is a bit of another story as I had to replace the coil to get an even tach input to the MS, the old high output coil not wanting to play. I fitted a coil for use with a ballast resistor as it wouldn't run with any other, even though I could find no resistor and the coil receives 13volts. However, if it was spark I would have thought that it would misfire at higher rpm first, and how come it starts again immediately.
No indication it is fuel related, would have thought if the fuel pump was faulty it would not die for a second then come back, as witnessed by the fact I can jump start it straight away it's died.
The MS is still opening injectors when it happens and if it was stalling under alternator load it wouldn't hold a steady 900 at rest and then just die.
Any and all thoughts welcome !
No problems when driven for less than 30 minutes, seems to need a really good warm through before the issue appears, also only when cooling fan running (only have 1 at the moment) and coolant at 90 degrees.
Symptoms are when changing down or coming to a halt (so revs below 2000, clutch depressed) the engine dies, no stutter just stops. If speed high enough will allow jump starting although revs then need to be kept at 1500 plus or will stall again.
Sitting at idle in the garage everything will be fine, 900 rpm fairly even, 14.5 - 15 AFR, cooling fan on constantly but holding 90. No warning will suddenly die. Will start immediately but needs 1500 held or dies again. After a a short while will idle ok again.
Initially I thought maybe the coil as it does get hot, however it is brand new. This is a bit of another story as I had to replace the coil to get an even tach input to the MS, the old high output coil not wanting to play. I fitted a coil for use with a ballast resistor as it wouldn't run with any other, even though I could find no resistor and the coil receives 13volts. However, if it was spark I would have thought that it would misfire at higher rpm first, and how come it starts again immediately.
No indication it is fuel related, would have thought if the fuel pump was faulty it would not die for a second then come back, as witnessed by the fact I can jump start it straight away it's died.
The MS is still opening injectors when it happens and if it was stalling under alternator load it wouldn't hold a steady 900 at rest and then just die.
Any and all thoughts welcome !
14.5 - 15 AFR Seem's quite weak, mine runs best at 13.6 anything over 14 it starts to get lumpy. also with the extra heat, it's going to be even weaker.
Also have you check the loads sites for the TPS and rev's its cutting out at.
The load and idle need to be set-up hot 1st, then after re-set from cold, with cold adjustments in the cold enrichments not on the load sites. (well this is true on the emerald)
You may want to ask for some help on the MS forum. as sounds more ECU related than the engine or car.
Also have you check the loads sites for the TPS and rev's its cutting out at.
The load and idle need to be set-up hot 1st, then after re-set from cold, with cold adjustments in the cold enrichments not on the load sites. (well this is true on the emerald)
You may want to ask for some help on the MS forum. as sounds more ECU related than the engine or car.
keatsie said:
Can you try lightly revving the engine from idle and see if the revs drop or rise as expected. If the revs drop or the engine tries to die check the throttle pot, it could be on its way out - you would be missing acceleration enrichment and slow idle control.
Hi,Revving from idle is fine and the throttle pot sweeps ok, you can see the voltage change through MS. Accel enrichment is switched off and with no stepper motor idle control is purely a function of throttle stop position, bleed screw (fully closed) and injector pulse (controlled against MAP with MAT offset).
2mad said:
have you checked the cooling system for an air lock as the problem happens after half an hour and the cooling fan is coming on. the temp gauge could be under reading .this could confuse the ecu.
Hi,Pretty sure no coolant locks, fan cuts in before 30 minutes - cuts in at 82 deg dead according to the coolant temp sensore which appears to be reading spot on all the time (can see it direct through MS). Dying symptoms just only occur after everything thorougly warmed through.
TVRleigh_BBWR said:
14.5 - 15 AFR Seem's quite weak, mine runs best at 13.6 anything over 14 it starts to get lumpy. also with the extra heat, it's going to be even weaker.
Also have you check the loads sites for the TPS and rev's its cutting out at.
The load and idle need to be set-up hot 1st, then after re-set from cold, with cold adjustments in the cold enrichments not on the load sites. (well this is true on the emerald)
You may want to ask for some help on the MS forum. as sounds more ECU related than the engine or car.
Hi,Also have you check the loads sites for the TPS and rev's its cutting out at.
The load and idle need to be set-up hot 1st, then after re-set from cold, with cold adjustments in the cold enrichments not on the load sites. (well this is true on the emerald)
You may want to ask for some help on the MS forum. as sounds more ECU related than the engine or car.
Just the fumes smell a bit at anything slightly rich, it is a bit lumpy but doesn't falter at all, when it dies it stops quicker than the ignition being switched off.
Using MAP rather than TPS - would you recommend changing ?
It's cutting out at 35kpa when changing down but also at 50 kpa when idling where the bins are sufficient to give the AFR mentioned. Overrun fuel cut off is switched off but I noticed it does run very weak on the overrun so maybe need to load up low kpa / low rpm but still doesn't explain the dying whilst idling and inability to hold an idle immediately afterwards. It definitely seems more like a condition that exists then clears but will try setting up a richer idle.
Process for set up sounds the same, will query on the MS forum also but I thought it might be more of a wedge idiosynchrasy rather than MS.
Thanks for the suggestions (everyone).
crackedfinger said:
Do you still have an ignition amplifier? I had the same symptoms which were cured by replacing this part.
Hi,Yes, fuel only at this stage so still using original distributor / coil. I did think about this intermittently failing as it would cause this symptom but too much of a coincidence in that it would only fail when less than 2000rpm, highish vacuum ?
chunder said:
crackedfinger said:
Do you still have an ignition amplifier? I had the same symptoms which were cured by replacing this part.
Hi,Yes, fuel only at this stage so still using original distributor / coil. I did think about this intermittently failing as it would cause this symptom but too much of a coincidence in that it would only fail when less than 2000rpm, highish vacuum ?
crackedfinger said:
chunder said:
crackedfinger said:
Do you still have an ignition amplifier? I had the same symptoms which were cured by replacing this part.
Hi,Yes, fuel only at this stage so still using original distributor / coil. I did think about this intermittently failing as it would cause this symptom but too much of a coincidence in that it would only fail when less than 2000rpm, highish vacuum ?
Even though the MS "sees" this as a tach signal no way of telling even reviewing a datalog as the tach signal will die the same time revs actually die. As stated before it does appear to be an intermittent failure and a condition change rather than something that builds up, loss of spark would cause this symptom.
Does anyone know the correct part number for the coil ?
Assume the ignition amp is Lucas DAB118 ?
I don't have a V8 Wedge but....
You could have a lean miss during idle(hydrocarbons high)
The load of the release bearing could be just enough to "nudge" the timing and cause a stall.
If you have a gunsen tester or similar get a hydrocarbons reading, richen the idle, if your hydrocarbons go down (yes down) then you had a lean miss.
Best to check the simple stuff first.
You could have a lean miss during idle(hydrocarbons high)
The load of the release bearing could be just enough to "nudge" the timing and cause a stall.
If you have a gunsen tester or similar get a hydrocarbons reading, richen the idle, if your hydrocarbons go down (yes down) then you had a lean miss.
Best to check the simple stuff first.
jeff m said:
I don't have a V8 Wedge but....
You could have a lean miss during idle(hydrocarbons high)
The load of the release bearing could be just enough to "nudge" the timing and cause a stall.
If you have a gunsen tester or similar get a hydrocarbons reading, richen the idle, if your hydrocarbons go down (yes down) then you had a lean miss.
Best to check the simple stuff first.
Hi, I have a wideband O2 sensor providing closed loop control to the MS and also a second output to a dash mounted gauge and AFR does go richer if I richen at idle. You could have a lean miss during idle(hydrocarbons high)
The load of the release bearing could be just enough to "nudge" the timing and cause a stall.
If you have a gunsen tester or similar get a hydrocarbons reading, richen the idle, if your hydrocarbons go down (yes down) then you had a lean miss.
Best to check the simple stuff first.
Thanks for the suggestion !
Check ignition amp. Stick a strobe on an HT lead, rev it whilst firing the strobe. you'll see a nice series of flashes. then let the engine idle and watch the flashes as it dies. You might see that as you approach idle, the flashes become weak and intermittent and then the engine dies - sign of a dying ignition amp. 'Swot mine did.
Where do you live? Anywhere near Basingstoke?
Ed.
Ah, Australia. Hmm. Bit far for me to drive out! Still, I would suspect igm amp. What you are seeing is the early stages of failure, I think. Same as mine did, and a new one cured it.
Where do you live? Anywhere near Basingstoke?
Ed.
Ah, Australia. Hmm. Bit far for me to drive out! Still, I would suspect igm amp. What you are seeing is the early stages of failure, I think. Same as mine did, and a new one cured it.
Edited by ed_crouch on Tuesday 17th August 18:46
chunder said:
I fitted a coil for use with a ballast resistor as it wouldn't run with any other, even though I could find no resistor and the coil receives 13volts.
Even with a ballast in, the coil would appear to your multimeter to be receiving 13v... because, well, it is. Until the ignition amp starts firing the '-' side of the coil, the LT circuit is open-circuit. The input impedance of the meter coupled with the coil effectively not being there means that the meter will see 13v. If you used an 'old-fashioned' analogue multimeter, the meter itself would present more of a load to the resistor so you'd get a truer reading of the voltage (probably still more like 11v or so).Doesn't explain why you can't find a ballast or any of the other issues, but I thought you might like an electronics lecture
chunder said:
anyone else had an intermittent failure like this - any way the part can be tested ?
If you mean the ignition amplifier module? Yes!Just been re-reading the whole thread and because it appears to be intermittent heat-related failure the suggestions are variously pointing at both fuel AND sparks. Even the cooling system is suggested.
And so it becomes a random shotgun search for - What? I cant see any pattern!
Sometimes though, when up to one's arze in alligators, its easy to lose sight of an urgent need to drain the swamp. "Back to basics" can often uncover root causes.
So it seems here, that as a starting point, a full ignition system check will become inevitable.
What follows then, is a collection of parallel RV8 universe forii wisdoms compiled into a systematic ignition test program, for every component, in the generic RV8 mid '80's ignition fitted to the RV8 Efi SD1. It should be adaptable for similar amplifier systems.
TESTNG IGNITION COMPONENTS - BACK TO BASICS
The circuit represents BOTH the system where the amplifier is mounted in an aluminium housing behind the coil AND where it is mounted on the side of the distributor. The effective electrics are the same, just the physical locations of components differ.
Be sure the earths and the wiring from the ignition switch through to the coil, distibutor and amplifier module are pretty much the same as shown.
Getting Started
o Reasons for testing the ignition system are a proven loss of sparks at the spark plugs, or weak/intermittent sparks causing misfiring.
o To proceed, separate the Low and High Tension circuits to find out immediately which circuit is faulty, then persue the fault condition in either circuit according to the results of some logical tests.
o Remove the king lead from the distributor, connect it to a good spark plug and lay the plug on the engine somewhere.
o Switch on the ignition and crank the engine.
o Is there a fat spark at the spark plug.
o If Yes - then the problems are downstream and away from the king lead at the dizzy cap, rotor arm, plug leads, plugs, or ignition timing so that is where to look - see " Other Components" (later) for checking the usual suspects, inspect, clean, substitute and only replace if faulty.
o If No - change the king lead.
o If still No - then the problems are upstream from the king lead and towards the coil, amplifier, distributor innards or their local connections all the way back to the ignition switch.
Testing the Low Tension Side Voltage Feed
o Switch on the ignition and use a multimeter to verify there are 12 volts at coil positive.
o If No - find out why, by checking the circuit between coil positive and the ignition switch and beyond, all the way back to the battery if necessary, for corroded or loose/broken connections.
o If Yes - dont take it for granted, waggle local wiring and toggle the ignition switch a few time to ensure the voltage is reliable, even using a bright lamp to check the wiring can supply a load.
Test the coil independently
o Disconnect the wire from coil negative to the amplifier.
o Turn ignition on, and strike coil negative to earth with a flying lead to see how good is the king lead spark.
o If sparks are absent/poor/weak and +12 volts is still present at coil positive then the coil is prime suspect for inspection/replacement.
o If sparks are fat/healthy then coil must be OK, so look for amplifier/pickup coil problems.
Test the Amplifier and Distributor Pickup Coil Together.
o Remove Distributor Cap.
o Disconnect ECU trigger wire from the 6.8k ohm resistor to prevent spurious signals getting to the ECU.
o Disconnect amplifier wire from coil negative.
o Connect a 12v 21W bulb from the same amplifier wire to coil positive (12 volt supply).
o The 21W bulb acts as a substitute coil load.
o Turn ignition on and rotate distributor rotor arm back and forward against the vacuum/mechanical advance springs.
o As the toothed reluctor wheel triggers the pickup coil, the amplifier should flash the bulb.
o If bulb flashing is positive and consistent the amplifier and pickup coil are working correctly together.
o If lamp does not flash or is inconsistent/weak either the amplifier or pickup coil is faulty.
Check the pickup coil independently
o Remove the amplifier connections to the pick-up coil and measure the resistance of the distributor pickup coil for a steady value between 500 ohms to 1500 ohms on the ohm-meter. Flex the wires at the same time to test their integrity.
o Outside the above range, short or open circuit indicates a croaky pickup coil.
o By process of elimination, if the pickup coil is OK, one might conclude the amplifier is faulty but nothing is ever that simple with electronic components, so to be sure:
Test the Amplifier independently
o What follows is an elegant but slightly complex test process.
o Use a 1.5 volt pen-cell battery connected in series with a (say} 2,700 ohm resistor and two flying leads to simulate the pickup coil.
o With the coil and amplifier connected normally and the distributor pickup coil disconnected from the amplifier, connect one flying lead to one of the amplifier input connectors and touch the other flying lead intermittantly across the second amplifier input connector.
o This emulates a pulsed input thereby activating the amplifier in sympathy to generate sparks from the coil?
o Polarity of this simulation is non-critical as neither flying lead is connected to earth, only to the amplifier input connectors, and the pulsing voltage from the pen-cell via the 2700 ohm resistor acts similar to the pickup coil input without causing stress or damage to the amplifier.
o The above test can be performed with the 21 watt bulb as the coil substitute as previously described, except in that circumstance, the pick-up coil simulation will flash the bulb.
Alternatively (for even more elegance), going one step further:
o Construct a small test box complete with switch, 21 watt bulb/holder, pen-cell battery, 2700 ohm resistor, 12 volt pos/neg power connections (from a car battery), spade connectors to the amplifier, etc.
o Connect up the 12 volts power and the amplifier to the test box and flick the switch repeatedly to emulate the pulsed input from a pickup coil and see the 21 watt bulb flash in sympathy to show the amplifier is working correctly.
Other Components
o Another possible component failure will be the suppressing condenser breaking down under the back-EMF from the coil.
o Remove condenser from circuit to see if the problem disappears.
o If yes, replace the condenser.
o Almost finally! For all the previous components check the LT wiring is not corroded, broken, dodgy or otherwise failing.
o Because all the components upstream of the king lead now check out OK, if fat sparks emerge from the king lead but not at the spark plugs its time to review the downstream components to see if they are dragging down, or failing to conduct, the Hi-Tension energy.
o Rotor arm - inspect for carbon tracking, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress.
o Distibutor cap - inside and outside - inspect for carbon tracking, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress. Wipe completely clean and shiny, especially between the turrets.
o Plug Leads and Hi-tension connectors - inspect for breaks and contact damage, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress. Wipe completely clean and shiny.
o Spark Plugs - Check for recommended type, clean and gap to correct spec, inspect for insulator damage externally and whiskering/crud between central contact and body. Clean externally to a shine.
o The above four items are "zero cost" actions. Many owners replace them all never knowing which of the components may have been faulty.
o Check by swapping is an easy process before buying replacements.
o Looking for spark tracking on a dark night generally reveals faulty hi-tension parts.
Work in Process, Errors and omissions - please advise.
If and/when the voracity of the ignition system is established and the problem still exists, time to move on to a full and systematic check of all the Efi components.
Being unfamiliar with the Efi system on your car, means one can only point to such component descriptions/tests that exist in this archive that could be common to your system, and suggest a cherry picking test session accordingly.
If after all the above, the intermittent failure persists, then a dynamic check of the ignition system is called for.
Guaranteed Foolproof Intermittent Ignition Fault Finder.
Rig up two 4/5 watt 12 volt bulbs (or better still, 2V, 15mA LED's + 680 ohm resistors) on test leads into the cabin and connect one between coil +ve and earth and the other to coil -ve and earth. Mark the bulbs POS and NEG. Beware cables dont foul hot/moving parts.
Start the engine and observe:
POS sensing the ignition input voltage is permanently on,
AND
NEG sensing the pulsed voltage across the Ignition Amplifier flickers in sympathy with engine rpm, or is dimly lit (LED's flicker better).
Now drive the car and have a helper note what happens when the engine misbehaves.
If POS and NEG go out together there is an open circuit interruption of the 12 v feed such as a faulty wire/ignition switch,
OR
A short on the same circuit due to burned insulation.
If NEG comes full on the Ignition Amplifier (due to excess internal heat) or its associated wiring/earth has failed in open circuit mode,
OR
The pulsed input (ie Hall Effect or Reluctor) to the amplifier from the dizzy has failed or the associated wiring is faulty/shorting to earth,
OR
The Coil has failed in a short circuit mode (unlikely cos it would surely kill the amplifier methinks?)
If NEG goes out the Ignition Amplifier has temporarily failed in short circuit mode due to excess internal heat,
OR
the local wiring is shorting to earth,
OR
The coil has failed in open circuit mode due to insulation breakdown or internal heat
If POS stays lit and NEG show signs of flickering instabilitynot sympathetic with engine rpm, then the Ignition Amplifier or its connections are on the blink.
Not the most elegant test process, but with alligators now joined by crocodiles, deperandum rules!
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