Extended cranking time cold start
Discussion
Hi
any thoughts or suggestions on this.
Standard late 94 Griffith 500, cold start cranking time has gone from 1-2 seconds to at least 5-6 over the last few weeks and seems to be getting worse.
I've done the usual checks, no ECU codes, checked for vac leaks with carb cleaner and blocking of various hoses to the plenum, non found. Checked fuel pressure, 40 psi key on and when cranking all good, keyed on off fuel pump a few times before starting no change. Checked ECU coolant temp on ECUmate all good same readings as ambient and fuel temp sender. Battery fully charged and good cranking speed. What did make a difference was carb cleaner into plenum chamber, fired up almost instantly. So seem to have a lean mixture on cold start up, thinking a fuel enrichment thing going on not an air leak. I assume spark is fine as hot starting and starting with carb cleaner is no issue but have not actually checked spark condition.
Any one had a similar experience? maybe fuel injectors past their best?
Any help appreciated.
Ozstyle
any thoughts or suggestions on this.
Standard late 94 Griffith 500, cold start cranking time has gone from 1-2 seconds to at least 5-6 over the last few weeks and seems to be getting worse.
I've done the usual checks, no ECU codes, checked for vac leaks with carb cleaner and blocking of various hoses to the plenum, non found. Checked fuel pressure, 40 psi key on and when cranking all good, keyed on off fuel pump a few times before starting no change. Checked ECU coolant temp on ECUmate all good same readings as ambient and fuel temp sender. Battery fully charged and good cranking speed. What did make a difference was carb cleaner into plenum chamber, fired up almost instantly. So seem to have a lean mixture on cold start up, thinking a fuel enrichment thing going on not an air leak. I assume spark is fine as hot starting and starting with carb cleaner is no issue but have not actually checked spark condition.
Any one had a similar experience? maybe fuel injectors past their best?
Any help appreciated.
Ozstyle
How long have you had the car?
I've had similar problems with various cars caused by extreme weather conditions/temperatures.
As a test, have you considered adding a resistor into the temperature sensor circuit when the engine is cold to see if it starts better, you will need to check what the resistance of the sensor is when cold and hot and then select a suitable resistance value for connection in series or parallel with the sensor that will higher or lower its resistance and alter the ammount of fuel injected when cold, you could use a variable resistor to carry out some tests
If you do come up with the ideal resistance/resistor to cure the cold start problem you can wire that resistance into the temperature sensor circuit so that it only connects when operating the starter motor, this is a cold start modification that has saved me much grief in the past
Someone else may be along shortly that is aware of the fault, the injectors could be the cause the problem
If all else fails you could try the above cold start test
I've had similar problems with various cars caused by extreme weather conditions/temperatures.
As a test, have you considered adding a resistor into the temperature sensor circuit when the engine is cold to see if it starts better, you will need to check what the resistance of the sensor is when cold and hot and then select a suitable resistance value for connection in series or parallel with the sensor that will higher or lower its resistance and alter the ammount of fuel injected when cold, you could use a variable resistor to carry out some tests
If you do come up with the ideal resistance/resistor to cure the cold start problem you can wire that resistance into the temperature sensor circuit so that it only connects when operating the starter motor, this is a cold start modification that has saved me much grief in the past
Someone else may be along shortly that is aware of the fault, the injectors could be the cause the problem
If all else fails you could try the above cold start test
As you have Rovergauge it would be interesting to look at the injector time for the first few cranking seconds-I think the ECU simply pulses the injectors enough to get the engine started, before switching the the AFM readings to get the correct amount once the engine has started. The fuel rail should hold its pressure after the pump has primed so you get an instant start. If the pressure drops it could delay the start for a second or two as the pressure rebuilds, but your time period sounds a bit long for this. If you can get or borrow a noid light to sit on one of the injectors you could check for the injector pulse on start up.
All,
Haynes/Rover manual states fuel regulator controls fuel pressure at 2.4 - 2.6 bar (about 36 psi) above manifold pressure, so happy with fuel pressure readings. Pump primes and gives 40 psi instantly, when priming stops it drops to 38 psi. 40 psi indicated when cranking and settles at 32 psi when engine idling. Fuel pressure holds when pump turned off, takes several hours to drop to about 20 psi.
Had the car 13 years and never had this issue, serviced my self, spark plugs and leads 6 months ago. The rotor arm, cap, coil, ignition module replaced over recent years with genuine lucas/bosch items.
As I'm in Australia extreme cold weather is not something I have to contend with, a coldest start for me is about 5C, this site has always been a valuable source of info and help when needed.
I only have an ECUmate not a Rovergauge so can't check injector pulse. Will look into a noid light.
thanks
Haynes/Rover manual states fuel regulator controls fuel pressure at 2.4 - 2.6 bar (about 36 psi) above manifold pressure, so happy with fuel pressure readings. Pump primes and gives 40 psi instantly, when priming stops it drops to 38 psi. 40 psi indicated when cranking and settles at 32 psi when engine idling. Fuel pressure holds when pump turned off, takes several hours to drop to about 20 psi.
Had the car 13 years and never had this issue, serviced my self, spark plugs and leads 6 months ago. The rotor arm, cap, coil, ignition module replaced over recent years with genuine lucas/bosch items.
As I'm in Australia extreme cold weather is not something I have to contend with, a coldest start for me is about 5C, this site has always been a valuable source of info and help when needed.
I only have an ECUmate not a Rovergauge so can't check injector pulse. Will look into a noid light.
thanks
Plugged in a noid light and all good, light pulses when engine cranking.
Sprayed a touch of carb cleaner into plenum just to double check and it fired straight away from cold, died after a second or so, started again and it fired up and ran.
At the moment still thinking dirty fuel injectors, I have a spare Rover ECU so may try that to see if there is any difference.
Sprayed a touch of carb cleaner into plenum just to double check and it fired straight away from cold, died after a second or so, started again and it fired up and ran.
At the moment still thinking dirty fuel injectors, I have a spare Rover ECU so may try that to see if there is any difference.
This does not make sense- you have good fuel pressure, and the niod light shows the injectors firing the moment you turn the key, so you should have fuel for ignition. I suppose really dirty injectors might not atomise the fuel enough for it to combust until the inlet was heavily full of fuel vapour?
its got me perplexed,
everything points to a lean mixture on cold start,
if it's not poor fuel atomisation, its either insufficient fuel delivery or an air leak,
so back to basics, check again for air leaks into plenum/inlet manifold, coolant temp sensor output and check spark condition on cranking, (already checked fuel pressure 3 times).
any thing else?
everything points to a lean mixture on cold start,
if it's not poor fuel atomisation, its either insufficient fuel delivery or an air leak,
so back to basics, check again for air leaks into plenum/inlet manifold, coolant temp sensor output and check spark condition on cranking, (already checked fuel pressure 3 times).
any thing else?
I know from experience the engine will still start with quite a big air leak as it does not rely on airflow reading for about the first 4 seconds, it just throws in a predefined amount of fuel to get the engine started and this is in excess of whats really needed. We know you have an injector pulse, just not how long but you can clearly see the shift in injector pulse timing with a 'scope if you have access to one?. This is a back to basics- do you have access to an old world colour tune? You can look for spark and combustion colour with one and see whats really going on? Also worth popping a strobe on there just to check you are getting HT on initial cranking.
well checked for air leak again, hot engine at idle and stepper motor connector removed, sprayed starter fluid all over plenum connections, afm to plenum air hose connections, stepper housing, vac hose connections, throttle housing/spindle, throttle heater plate, plenum/air stack joint, air stack/manifold joint, fuel injector seals, manifold inlet valley; absolutely nothing, no air leaks detected.
Checked for spark on cranking, it's there, steady white spark on tester from those ignition leads tested.
Tester indicated steady spark, at about 25kv from at king lead from coil, about 20kv at ignition leads from distributor cap.
No recent work done on the engine that could have influenced fuel enrichment.
Dizzy cap, rotor arm, module all genuine items and only 5000+ km or so on them, ignition leads new last year.
No air leaks, got spark, got injector pulse, and fires straight up with a little squirt of starter fluid in the plenum.
? fuel flow
Checked for spark on cranking, it's there, steady white spark on tester from those ignition leads tested.
Tester indicated steady spark, at about 25kv from at king lead from coil, about 20kv at ignition leads from distributor cap.
No recent work done on the engine that could have influenced fuel enrichment.
Dizzy cap, rotor arm, module all genuine items and only 5000+ km or so on them, ignition leads new last year.
No air leaks, got spark, got injector pulse, and fires straight up with a little squirt of starter fluid in the plenum.
? fuel flow
from retired ex Auto sparks, the sensor that adjusts the Fuel pulses...ie...richer for Cold is in the inlet manifold [ pic of sensor hear ] its the 2 pin one, don't confuse with the " single pin one", that's the Temp Dash https://www.racetechdirect.co.uk/img/product/E0376...
The KV is very high- this tends to imply there is an open circuit somewhere in the HT system- you dont need anything like 20kv to start the arc at cranking- 12kv would be more typical on the lead, or lower with Magnecores. Just an observation. As for temp sensors- the impedance of the one on the fuel rail and the water temp are the same (as is the connectors) so if you can get the leads to reach you can swap them over and see if it makes a difference. This really sounds like the ECU is not putting in the correct injector pulses for starting (I think it double pulses) but to have a fault like this would be so strange as its part of the ECU programming. The information is buried here somewhere if you dig around for the 40 odd page post for programming the 14cux.
https://www.pistonheads.com/gassing/topic.asp?t=13...
If you want to check the fuel pressure on cranking a mechanical oil pressure gauge works well on a bit of fuel hose if you have a serp engine- but you have to remove the valve first from the take off point. Pre serps are a pain, as you have to put a T piece in the fuel line before it enters the fuel rail.
https://www.pistonheads.com/gassing/topic.asp?t=13...
If you want to check the fuel pressure on cranking a mechanical oil pressure gauge works well on a bit of fuel hose if you have a serp engine- but you have to remove the valve first from the take off point. Pre serps are a pain, as you have to put a T piece in the fuel line before it enters the fuel rail.
Edited by blitzracing on Saturday 12th May 21:19
All ready used fuel pressure gauge on the fuel rail, getting 40 psi when cranking.
Sure about KV Blitz being too high ?, general comments on internet indicate figures are ok.
Regardless, for this issue, indicates good HT pulse delivered to spark plugs when cranking, so lack of spark not an issue.
As for ECU coolant temp sensor, checked when cold using ECUmate, all good, giving same temp as ambient air temp and same as the fuel temp sensor reading. I checked wiring colours to both sensors and match that of rover wiring diagram.
As said in prior message, fuel pressure holds in line for several hours; so no fuel leaks in line or connections that could be drawing air into system, checked fuel line connections and fuel pump for any leaks also, non found.
I'll check base idle, clean stepper, pull a few spark plugs (fairly new) for further checks. (Still need to check with spare ECU)
Sure about KV Blitz being too high ?, general comments on internet indicate figures are ok.
Regardless, for this issue, indicates good HT pulse delivered to spark plugs when cranking, so lack of spark not an issue.
As for ECU coolant temp sensor, checked when cold using ECUmate, all good, giving same temp as ambient air temp and same as the fuel temp sensor reading. I checked wiring colours to both sensors and match that of rover wiring diagram.
As said in prior message, fuel pressure holds in line for several hours; so no fuel leaks in line or connections that could be drawing air into system, checked fuel line connections and fuel pump for any leaks also, non found.
I'll check base idle, clean stepper, pull a few spark plugs (fairly new) for further checks. (Still need to check with spare ECU)
blitzracing said:
The KV is very high- this tends to imply there is an open circuit somewhere in the HT system- you dont need anything like 20kv to start the arc at cranking- 12kv would be more typical on the lead, or lower with Magnecores. Just an observation. As for temp sensors- the impedance of the one on the fuel rail and the water temp are the same (as is the connectors) so if you can get the leads to reach you can swap them over and see if it makes a difference. This really sounds like the ECU is not putting in the correct injector pulses for starting (I think it double pulses) but to have a fault like this would be so strange as its part of the ECU programming. The information is buried here somewhere if you dig around for the 40 odd page post for programming the 14cux.
https://www.pistonheads.com/gassing/topic.asp?t=13...
If you want to check the fuel pressure on cranking a mechanical oil pressure gauge works well on a bit of fuel hose if you have a serp engine- but you have to remove the valve first from the take off point. Pre serps are a pain, as you have to put a T piece in the fuel line before it enters the fuel rail.
There's a bit of info on injector pulse rate here:https://www.pistonheads.com/gassing/topic.asp?t=13...
If you want to check the fuel pressure on cranking a mechanical oil pressure gauge works well on a bit of fuel hose if you have a serp engine- but you have to remove the valve first from the take off point. Pre serps are a pain, as you have to put a T piece in the fuel line before it enters the fuel rail.
Edited by blitzracing on Saturday 12th May 21:19
https://www.pistonheads.com/gassing/topic.asp?h=0&...
You'll need RoverGauge to dump out the PROM contents to check if the code has been corrupted - but I doubt it has.
Some 'tuners' chips have extended cranking time to allow for oil circulation prior to firing.
Gassing Station | Griffith | Top of Page | What's New | My Stuff