A reluctant Starter - Now Sorted by S & C

[Piers300]

Hi Lee

Thanks for the advice. I will try and find your other threads and have a read. I have never tried to balance the RBTB's or adjust the voltage of the TPS before, so will need to do some reading and a phone call might be very useful next week. One thing I do have left over from my old Super Sprint with twin 40 DCOE's is an air flow meter, which looks like it will come in handy.

Piers

[John Vine]

There's a Minister guide to setting up RBs here.  It refers to a TPS resistance at idle of 0.45 ohms,   That puzzles me as the guidance CC sent me (WN373) quotes 0.43-0.45v.  If you'd like a copy of WN373, just send me a message with your email address.

JV

[garybee]

 

 Do you get a vacuum whoosh when you open the filler cap? That was a symptom of my fuel starvation problem. Peter

 

That will only be an issue with cars that have been running for a while.  When starting a car it doesn't have time to pull a significant vacuum in the tank.

 

[Piers300]

Dave J. I just tried disconnecting the air temp and water temp sensors in turn and no difference.

The next thing is to do the TPS resistance check and check the balance. That will have to wait till Friday.

Thank you everyone for responses.

 

Piers

[john milner]

Could the petrol in the tank be contaminated? A squirt of good stuff to get it going and when running it tolerates the bad.

[Piers300]

A new Banner battery and fuel filter arrived today and both will be fitted over the weekend. If these don't crack the problem, the final thing is checking the TPS resistance.

 

Piers

[Jonathan Kay]

It refers to a TPS resistance at idle of 0.45 ohms,   That puzzles me as the guidance CC sent me (WN373) quotes 0.43-0.45v.

Apart from the actual values I'd like to know why some recommend using a resistance setting and some a voltage setting. Is it because of the imperfect voltage regulation of the whole system?

Jonathan

 

 

[elie boone]

I think that a Ohm measurement is more stable than a voltage measurement, because the out put voltage measured depends on the input voltage,that is why the voltage has a wider band.

[Bottrill]

Let us know how you get on with the battery, Piers. I have my Banner hooked up to a CTEK charger but tonight I had a struggle. I need to check the cranking voltage. The battery nearly died by the time car caught and fired up, I think it must have heard me talking about it over the past two days!

Here is the link to the TPS page I have mentioned. Apologies if I'm teaching you to suck eggs so to speak. 

Www.enduringautomotive.com/tps

 

Lee

[Piers300]

Lee  Thanks for the link on the TPS. I hope to get some time in the garage tomorrow or Sunday. Unfortunately, mowing comes first and then teak oiling the garden tables and chairs.

I have to fit the new battery, fuel filter, check the TPS and check the connection in the multipin plug below the t/b's.

Thanks again

 

Piers

 

 

[Paul Deslandes]

That resistance value simply cannot be correct as the average multimeter cannot measure such low resistances with any accuracy, if at all. 

The ECU senses TPS voltage and, IMHO, the TPS should be adjusted for the correct voltage setting at idle.  All ECUs have a well regulated reference voltage for the TPS which is more than sufficiently stable across the temperature and source voltage ranges for accurate TPS load site sensing.

TBH, even amongst those that find electrics difficult, voltage is fairly well understood, however ohmic resistance less so.  0.45 Ohms is about the same as the resistance of the test leads by the time contact/connector resistances are included. Just try setting your multimeter to the low Ohms range and short the probes together and see what it reads.  I suspect that ohms has been used when voltage was what was meant.  Either that or it should have read 0.45k Ohms (or 450 Ohms).

Paul

[Jonathan Kay]

Thanks, Paul.

Jonathan

[Piers300]

Well after a rather good weekend of Kent County Show yesterday, Wimbledon and F1 this afternoon, plus quite a few hours in the garage I will bring you up to date, I replaced the battery with a new Banner even though the old one is six plus years old and reading 13 volts when removed from the car. 

i then set about the t/b's and tried to adjust the opening to 1mm on each barrel. I then checked the resistance of the TPS and got a reading smack on what it is meant to be. I then started the car having to use the squirt of fuel in each barrel and using the synchroniser, checked the air flow and that was also spot on.

Finally, I changed the in line fuel filter and what a faff that was. I got it done and I started the car. It was a bit rough to start with and then it settled down. I then left it to cool down, watched the F1 and took the dog for a walk. When it had really cooled, it started first turn of the key. I have to say I was mighty relieved, but the real test will be tomorrow morning.

Piers

[Piers300]

This morning, the car started on the second push of the start button and settled down into a smooth idle. I have to admit to being highly relieved and delighted at the same time.

 

Piers

[JNC]

Piers do you use a battery conditioner charger ? . I keep mine on condition charge all the time when it's in the garage . I use a Ctek 0.8 it keeps the battery at peek and starts my Duratec first time . When you think it's only a mower size battery it's a lot to ask IMO .

[Piers300]

John. Yes the old and new battery are on a conditioner when in the garage. When I took the old battery out, I measured with a certified Fluke 87 meter and it was 13 volts. The car had been running before hand hence the voltage but it is 6 plus years old, so that is pretty good. However the new battery cranks the engine faster.

 

Piers

[John Vine]

I visited my daughter and son-in-law at the w/e and took the opportunity to play with my old SS-R -- ah, the memories!

In case they may help others (and Piers!), here are some observations:

We measured the TPS voltage across pins 2+3 with the ignition on but engine not running.  With RBs closed, is was 0.42V (CC guidance 0.43-0.45v), and at WOT was 4.54V.  I don't know what map sites/values these voltages would correspond to, but it would be good to know.  (Pin 1 was the supply @ 5.01v.)

 

That resistance value simply cannot be correct...

To provide evidence for Paul D's statement, we measured the TPS resistance across pins 1+2 with the RBs closed as mentioned in the Minister guide (see above).  On the 20K ohm setting, it was 4.30:

This is 4,300 ohms (not the 0.45 ohms stated by Minister), so you were quite right, Paul.  For info, the WOT resistance reading was, IIRC, 0.5 (that is, 500 ohms).  So, the 4.30 pairs with the 0.42v above.  I'm wondering whether the resistance should maybe read 4.50 rather than 4.30 (and the voltage 0.43-0.45)?  If so, perhaps the TPS is set slightly on the low (weak mixture?) side? 

We next checked the RB balance.  We were surprised to see just a tiny gap under each barrel, much less than 1mm.  I was wondering whether this might have contributed to the poor starting, but S-in-L reported a steady tickover when warm of 1000rpm.  He also reported the airflow in each trumpet (measured with a synchrometer) to be pretty equal across all four.

Finally, we tried to start it (foot off the throttle).  It fired occasionally but was very hesitant to catch.  I wanted to assess the effect of a squirt of neat petrol in each intake, so removed the air filter.  Immediately, the car started and settled to a regular but low tickover (about 500 rpm).  With a blip of throttle this settled to a regular 1000 rpm.  So, we were left wondering whether the air filter was below par.  I believe it's the original Pipercross item that came with the SS-R upgrade, so is about 12 years old.  It's certainly been cleaned from time to time, but was in poor condition, with some of the internal foam beginning to disintegrate.  A new one's on order.  I'll report back on what effect it has.

JV

 

 

[Jonathan Kay]

Thanks, John.

Jonathan

[John Vine]

This morning, the car started on the second push of the start button and settled down into a smooth idle.

Piers, it sounds like you may have cracked it.  So, was it all down to the fuel filter?  If so, I'm surprised, given that it's only about 6k miles old, but perhaps you've picked up some fuel crud somewhere?

JV

[Jonathan Kay]

Glad it's working better, Piers.

When I took the old battery out, I measured with a certified Fluke 87 meter and it was 13 volts. The car had been running before hand hence the voltage but it is 6 plus years old, so that is pretty good. However the new battery cranks the engine faster.

I don't think you've given us the minimum voltage during cranking, and I find unloaded voltages very difficult to interpret between batteries.

At least two things were changed leading up to the improvement. Is the following a reasonable hypothesis:

1. The fundamental problem was low fuel flow during cranking.
2. The fuel flow during cranking may now be higher because there's now more voltage at the pump
3. The fuel flow during cranking may now be higher because the filter is cleaner?

Jonathan (Crossed with #44)

[Piers300]

Jonathan. The volts on start up with the old battery was 10.2. I have not measured the new battery yet.

 

Piers

[Paul Deslandes]

It would have been interesting to know if the fuel pressure was constant (and good) both before and during cranking as this is what ultimately determines fuel flow via the injectors.  If there was sufficient pressure to run the car once it eventually started and warmed up, assuming it wasn't running seriously lean it's a bit surprising that it wouldn't start.  However, a good result.  Might be worth getting the pressure measured again. This is usually 3 - 3.5bar but will depend on the injectors chosen v engine max power.  Minister should be able to tell what it should be, hopefully not in Ohms!!!

I still don't understand why Minister specify the TPS setting as Ohms rather than Volts, especially as the TPS potentiometer will have a tolerance of, say, 5% which could potentially (pun unintended) make the idle setting voltage, which is what the ECU reads to select the load site - not resistance, in error.

I'm assuming the ECU is locked so you can't get at the TPS voltage/load site curve to see at what voltage the site 0 to site 1 transition occurs.  Pity if so.

One last thought: is your air intake taken from within the engine bay or do you have the elephant's trunk which picks up from under the radiator and has an in-line air filter?  If the latter arrangement, they can pick up all manner of muck from the road which can seriously block the air filter.  The fact that this essential service item was overlooked by several 'professional' service agents cost one owner several thousands of pounds in engine rebuilds in search of lack of power.  Once it was removed and then replaced, the car went like stink.

Paul

[Rusty Nuts Garage]

Just measured my mate's Roadsport 150 and it was 4180 ohms.

 

cheers

Keith

[Jonathan Kay]

You have to have one in your hands (man)! 

:-)

The first place in the display only ever shows nothing or "1" (apart from the preceding negative sign). So it can read up to 1999. The decimal point moves to tell you where you are. As 1.999 ≈ 2 you can match the displayed value to the selected resistance range, as they all start with "2".

It's surprisingly difficult to explain rigorously but it works fine in practice. To my amazement the manual doesn't help much if you don't understand  the display already.

Shirley (Rita's cousin)

[Piers300]

Paul  -   When the car was picked up as a non runner, by the company who serviced it, they had ordered in a new in-tank fuel pump, because they thought it was either the pump or the relay module, which was replaced during the 6000 mile service. They tested the fuel pressure and said it was good.

The car is a standard 2004 R300 with a locked MBE 72908 ECU and standard injectors.

The air is taken from within the engine bay, via a Pipercross filter. I cleaned and washed the filter today, as I have a spare. I was going to fit it and I thought it was new, but it turned out to be dirty, but still in the CC packing. It came with the car when I bought it six years ago and because it was in the packing, I never really looked at it. I've got the foam filter cleaner and oiler left over from motor cycle Trials days, when you cleaned the bikes filter after virtually every trial. 

Piers