Cold start woes on a '72 FI auto

[n/a]

As a memory jog, this is the car with the unmarked motor that was in the threads about what casting numbers mean what and which cam was best to install after this one decided to eat a few lobes off a few months ago.

Well, it's back together, looks stock, but runs much better than stock.  Did an overbore and decked the block 1mm to keep the low comp pistons within 0.5mm of the deck at TDC.  Did a very nice port and polish job on the head and even worked the exhaust manifolds a little for flow.  We did end up using a -08 cam vs the eaten -05 cam and new cam followers.  The stock exhaust pipes are so tight you can feel the exhaust pulses six feet from the tailpipes at 4k.[:0]

Seems this car was left go and most of the FI systems stopped working some time ago.  Took nearly forever to get the motor to start even with priming the FI pump and lines.  Once started the factory timing setting of 8* ATDC with the vacuum line connected wouldn't keep it running.  Vacuum plugged and 15* BTDC and it runs great, max mech timing of 33 degrees with this distributor calibration.

Later found the fuel cutoff solenoid lead was taped up and didn't work even when hooked up.  Ended up soldering a short lead to the ground side of the solenoid and attaching it to the FI pump screw to get a good ground.  Once connected it would start right up once warmed, but still a bear to fire off first thing.  Couldn't get the A/F ratio adjusted with the FI screw either.

Chased it for a few evenings and found the thermostatic plunger on top of the FI pump was stuck keeping the car running pig rich all the time.  Went to MB for a new thermostat plunger and got a $54 price, went back home and played with the old one until it freed up and started working.  Tweaked that circuit until it ran clean warm and not too rich at idle cold.  FI pump screw works now.  All along I could never get the cold start fuel solenoid to fire until tonight. Seems MB's wiring circuit doesn't want it to fire unless the motor is below 62*F from the temp switch on the back of the head.

My question since my Haynes wiring diagrams just plain suck is there another way to make the cold start solenoid work besides jumping the temperature switch.  When jumped it fired right off cold and ran fine.  The temp switch is on the ground side of the cold start solenoid relay (not shown in Haynes [!]) and took some detective work to figure out.  After this it should be done.

Sorry so long, but BTW the car runs extremely strong and I'm proud to have figured out so much to make it run the MB way.

Jamie

'68 Ranchero GT '88 5.0 EFI 5-speed stock  

'93 Mustang LX hatch 5.0 5 speed, 10-1 CR, 73mm C+L MAF, SN92 Paxton, 3" SS power pipes, 65mm TB, Ported + Polished GT-40 intake, 24lb injectors, AFR 185's, 1.60 FMS rockers, Crane 2030 cam, Total Seal rings, SAAC valve covers, 1 5/8" BBK Longtubes, 2.5" custom X pipe, MAC 2.5" Catback 3" tips, 3.55 gears, ROH rims, Calypso green.

11.78 @ 118mph with 1.7 60' times, 390hp @ 5,800rpm and 400lbft @ 4,200rpm (Torque Monster 302)

Currently rebuilding a '71 SL

[A Dalton]

The cold start relay circuit is completed through the Thermo-time switch to ground [ switched ground]
 The feed for the relay is through the starter portion of the ignition switch, so it will only be energized in the start position.
 If one grounds the 'W" terminal on the TTS and the cold start works [ test lamp helps here] , then the TTS is suspect.
 Many users run a ground wire from this terminal to a swiched ground push button, momentary ON, in the cabin... kind of like the old manual choke, but electic...with this set-up, you are the TTS...advantage to this is you can operate the cold start squirter at will and as long as needed,[ only at crank], regardless of engine temp...
..like , when it won't start cuz it's hot [ common fault after sitting for 20 min...]
 Other plus is you do not have to worry about flooding fuel to engine when using the  starter  to turn engine over when doing valve adjust, dwell, and other repairs that require engine cranking w/ignition sw....

[ja17]

Hello Jamie,
Good job, I was wondering how you were getting along. A Dalton sums it up well. You probably have a bad temperature sensor or relay which activates the circuit when the starter is cranking. Try grounding the temperature sensor wires and see if the relay and starting solenoid begin to work. If not, the relay can be defective. Lastly someone may have wired it incorrectly.
The hot wire which feeds the solenoid originates at the fuse box and is switched onto the starting solenoid in the relay. The relay is activated by a hot line from the starter. The negative feed for the relay is switched on by the temperature sensor when it goes to ground.

Joe Alexander
Blacklick, Ohio

[n/a]

Thanks for the replies. From what I've read, the temp switch only closes below @68 degrees, it's open with this weather.  The relay is working when the temp switch is jumped across.  I wonder why MB designed it this way and what do I have to do to get the car to fire off cold without it.  I did take a shim out of the fuel side of the cold idle thermal plunger to clean it up at idle and wonder if it should have been left in (but it still didn't start easily).  I fear I may have another issue keeping the car from starting easily and just don't under stand their logic with this design.  Similiarly, why do I have to have the fuel cut off solenoid wired up so it starts easily warm?  Cutting off the fuel on decel isn't a very smooth or pleasant experience with this car / setup.  May even defeat that feature from the tranny switch.

Jamie

'68 Ranchero GT '88 5.0 EFI 5-speed stock  

'93 Mustang LX hatch 5.0 5 speed, 10-1 CR, 73mm C+L MAF, SN92 Paxton, 3" SS power pipes, 65mm TB, Ported + Polished GT-40 intake, 24lb injectors, AFR 185's, 1.60 FMS rockers, Crane 2030 cam, Total Seal rings, SAAC valve covers, 1 5/8" BBK Longtubes, 2.5" custom X pipe, MAC 2.5" Catback 3" tips, 3.55 gears, ROH rims, Calypso green.

11.78 @ 118mph with 1.7 60' times, 390hp @ 5,800rpm and 400lbft @ 4,200rpm (Torque Monster 302)

Currently rebuilding a '71 SL

[J. Huber]

Hello. Looking back on the thread, I don't believe anyone mentioned the Cold Start Valve. In my experience, the CSV is one of the first places to look for cold start issues. If it is doing its job, I would next test TTS located on the block. This is an important part of the start-up process. There are those who circumvent a faulty TTS but it is less than 100 bucks and easy to replace.

In addition to having the cold start system in order, having the points just right, the proper coil, and the right plugs seem crucial. Am I thinking too simplistic here? (be gentle...)

James
63 230SL

[n/a]

I'm a little illiterate on MB terminology so do be gentle and explain where the CSV and TTS are.  I chased the cold start fuel solenoid circuit and got it working once I jumped the temp switch on the drivers side of the head.  For ignition it's running electronic and the dwell meter reads 44 degrees and didn't care where it was set as long as the points touched.  Ignition is set at a base of 15 BTDC without the vacuum hooked up and runs beatifully once it starts.  It just doesn't want to put fuel to cylinders to start unless I jump out the temp switch to get the extra fuel solenoid to fire on the intake, then it fires right off.  This isn't that difficult of a system to figure out if you know EFI, just trying to figure out why MB did the systems and ciruits this way and how is it supposed to work.  I'm handicapped with a God aweful Haynes manual that tells you what to do, but not how or why.

Jamie

'68 Ranchero GT '88 5.0 EFI 5-speed stock  

'93 Mustang LX hatch 5.0 5 speed, 10-1 CR, 73mm C+L MAF, SN92 Paxton, 3" SS power pipes, 65mm TB, Ported + Polished GT-40 intake, 24lb injectors, AFR 185's, 1.60 FMS rockers, Crane 2030 cam, Total Seal rings, SAAC valve covers, 1 5/8" BBK Longtubes, 2.5" custom X pipe, MAC 2.5" Catback 3" tips, 3.55 gears, ROH rims, Calypso green.

11.78 @ 118mph with 1.7 60' times, 390hp @ 5,800rpm and 400lbft @ 4,200rpm (Torque Monster 302)

Currently rebuilding a '71 SL

[A Dalton]

What is the pump # Last 3 digits [ ie R22]
 Does it have 2 solinoids on the back ?

[n/a]

Last three on the pump is 'R24 Y' an it only has the one solenoid that 'wonderful' Haynes says is a fuel cut off solenoid, and it didn't work until I soldered a ground onto the rivetted ground head on the back of the solenoid and grounded it.  Today after work I chased another thing that bothered me.  The temp switch on the back of the head had two wires running to it and two 5mm screw terminals to connect them to.  I had removed one and got lucky and found the ground path for the cold start solenoids relay and 'guessed' that the other went to ground.  The more I thought about it I wondered if the thermal switch was actually two switches in one housing.  After removing both wires (one pink, the other pink/green) and ohming the terminals, I noticed one was 'grounded' and the other had resistance.  For testing purposes I swapped the wire connections out and was rewarded with the cold start circuit firing the car off within three seconds of the starter running and the fuel cutoff circuit wasn't as 'aggressive' on decel.  Took the car for a twenty minute run to get it up to temp and it ran great (does sound like a sewing machine with the hood off).  Got home shut it off for about an hour and tried to fire it back up only to get the dredded no start for about ten seconds.  Didn't check the condition of the thermal switch, but I'd guess it had 'switched' states.

I have a few days off to play some more, please stand by and feel free to comment.

[A Dalton]

<<<The more I thought about it I wondered if the thermal switch was actually two switches in one housing. After removing both wires (one pink, the other pink/green) and ohming the terminals, I noticed one was 'grounded' and the other had resistance. >>

 The switch is a thermal heater activated switch..The terminal with the resistance - [term G ]is a heater wound around a bi-metal type switch and completes to ground internally. . When it heats up, it causes the "W" terminal to open ..
[ the W terminal is normaly closed to ground when temp is less than 35C].  The time it takes to open is from 2-12 secs., depending on coolant temp .  [ a test for time calibration is it should open on a bench test at room temp of 20C in 5 secs when energized w/12v.]
 Anyway, this is the TTS and it is the switched ground for the Squirter [CSV] relay primary circuit. As in my previous post , if one wants to check the integrity of the CSV circuit, he may simply ground the W terminal at the TTS . That will complete the circuit to energize the relay coil, which in turn closes the relay contactor
[ load side of relay] to get 12v to the CSV via fuse #6. Because the start switch is in series with the circuit , the CSV will only work when the key is at start position. So, if the CSV works when grounding W , you know that the CSV,relay, and feed 12v are all OK, but the TTS is open. But is it open due to temp or is it shot? That is where the time/temp test comes in ..many still work, but cut-out prematurely ..ie too low a temp......
 I do not have color codes for the wires , but the W term will feed back to the relay term #85 and the G term will go to #86, so you can check that out via continuity for proper polarity..[pins 30 and 87 are the relay contactor/sw terminals]..
 You have the late style pump and they eliminated the starting solinoid that moved the rack foward for start assist , regardless of temp. So, on pumps without that feature , one can accomplish the foward movement of the rack by using the excelerator pedal...
 The reason guys run a ground sw in the cabin from the W terminal is because once the TTS excedes the temp spec, the CSV will not work.. but one can trump that with a little squirt.
 On a pump that has sat for an extended period, the ball valves leak back and the car will not start when warm, so the button will overcome this. I have seen many clear up after running/reseating for a while.
 { there was actually a Kit one could add that would energize the squirter fo 1-2 secs, regardless of engine temp, because of warm start problems with pump without the the extra solinoid]
 Anyway, there are other sensors and relay, but this is the basic CSV circuit..
PS ..the other pump solinoid is to bring the pump rack back to full lean status, an emmission device.

[J. Huber]

To clarify: the CSV (Cold Start Valve) is a starting aid located on the side of the intake manifold. I would be sure it is working right. There is a very simple leak test. On the side of the CSV there is a small 7mm (head) bolt for testing. Remove the bolt, and with a rag handy, turn the key to the point where the fuel pump is running (but don't turn over engine)... and watch the hole for a good 2-3 minutes. No fuel should come out. If it does, the CSV is probably gummed up or is just plain shot. I understand that a leaking CSV can do a lot of damage over time. In the short-term, it can cause starting issues (and lousy mileage).

Next I would test the TTS (with the engine as cold as possible). Mine was bad and since its replacement the car starts flawlessly. T,GD!



James
63 230SL

[n/a]

Excellent info guys, and I really appreciate it.  The concept of a heater, plus a temp switch in a coolant resevoir is a pretty novel idea.  I noticed that the 12vdc crank wire was pink as well as the ground, but didn't think to check for a connection to the TTS, just figured the extra wire was for another circuit.  I'm pretty sure it's hooked up correctly now, but am going to double check this afternoon.

{ there was actually a Kit one could add that would energize the squirter fo 1-2 secs, regardless of engine temp, because of warm start problems with pump without the the extra solinoid]

For that could I just unscrew the TTS from the block and ground it externally so the heater would work, but not be affected by the coolant temp?  I noticed it didn't want to start hot after sitting for an hour...

Jamie

'68 Ranchero GT '88 5.0 EFI 5-speed stock  

'93 Mustang LX hatch 5.0 5 speed, 10-1 CR, 73mm C+L MAF, SN92 Paxton, 3" SS power pipes, 65mm TB, Ported + Polished GT-40 intake, 24lb injectors, AFR 185's, 1.60 FMS rockers, Crane 2030 cam, Total Seal rings, SAAC valve covers, 1 5/8" BBK Longtubes, 2.5" custom X pipe, MAC 2.5" Catback 3" tips, 3.55 gears, ROH rims, Calypso green.

11.78 @ 118mph with 1.7 60' times, 390hp @ 5,800rpm and 400lbft @ 4,200rpm (Torque Monster 302)

Currently rebuilding a '71 SL

[A Dalton]

<<For that could I just unscrew the TTS from the block and ground it externally so the heater would work, but not be affected by the coolant temp?>>

 Well.. you then are sensing ambient temp and that is not what they are trying to accomplish .. the reason for coolant temp sensing is b/c all the other FI pump parameters are coolant temp sensed and are designed into the balance of fuel operations. [ ie.. you want all sensing inputs to be rom the same source]
 What I would do is to check and see if the TTS is switching at 35C as intended.[ bench test/previous test]
Bear in mind that Benz had designed the system to not need a shot from CSV once that coolant temp was reached for starting , but the pump before your [R22s] , also had a starting aide rack solinoid
that worked regardless of temp [ in other words , anytime the key was at start].
  So , they should start above 35C without help of the squirter [ CVS
slang for practicality] , but that means with  a perfectly trimed out a/f  pump, timing , etc ..
 Again, a cabin squirter to groung W works anytime you need it , but does not change anything in the system,b/c if you do not use it , the stock system is still there..
 

[George Davis]

The attached diagram shows the relay, TTS and CSV.  Late 280 SLs (70 and 71) don't have the starting magnet shown upper right, otherwise should be the same.  230 SLs are similar but not identical.  The circuit inside the "balloon" is not stock, but is easily added to give you control over operation of the CSV (as described by ADalton).

Download Attachment: CSV_relay_TTS.bmp
31.62 KB

George Davis
'69 280 SL Euro manual

[n/a]

Ok, good deal, the wires are now in the correct position and it's starting fine cold, warm, and even hot after sitting for a while.  Used it as a parts mule today around town to get a bunch of short runs in with 10-20 minute breaks in between.  Cold it takes about three revolutions of the motor to fire off.  Warm and hot are about the same.  This car gets almost as many looks as my blown '93 stang rolling around town (probally wonder where I stole it...)

Only downside of the car is if it sits at a red light for couple minutes idling it'll puff some blue smoke out as it pulls away.  Rings not totally seated?  Or worse?  I just don't want to turn over any problems to the owner.

Jamie

[A Dalton]

On the oil , a few things come to mind [ though may not be correct]
 One , the rings are not seated ...
 two, the crankcase oil is too full . [ they seem to like the  1/2 way mark]
 three, the R24 pump is lubed via crankcase oil feed and they use a little oil, as it is mixed w/gas..running for a while should clean the pump out and that will more likely get better..
I would also  check the breather pipe  and watch for the valve seals lifting up on the stems .. I know they are new , but have seen it happen [ usually resulting in oil foul plug on that jug..]
The last that comes to mind is that the ball studs have to be doped on these heads , as the threads go through to the head runners .
 I think it just has to be run........