Author Topic: More cold start valve issues (Read 22517 times)

ctaylor738 · « **on:** July 20, 2016, 01:07:04 »

I am working on a 250SL, back in my garage with hot start issues. Three years ago, I installed my timer-relay hot start solution (HSS) that fires the cold start valve for one second when the starter is engaged. This solved the problem (until now).

Now, the HSS is working electrically, but does not seem to be delivering any fuel to the cylinders. After attempts at a hot start, the plugs are bone dry. I removed the CSV and re-connected it putting it in a plastic bag. I observed fuel in the plastic bag after cranking. I tested the fuel pressure at the CSV and found it to be .7 bar. Spec is .8 to 1.1 bar. I put the valve on my injector tester, pressurized it to .7 bar and put 12V to it. The result was somewhere between a squirt and a dribble from the valve. Raising the pressure to 1.1 bar made it a little better but not exactly a spray.

So my theory is that the valve is releasing fuel into the intake manifold but it's not a spray and it's just running down to the bottom of the manifold and not making it to the cylinders to help with hot starting.

Oddly, no problems with cold starting.

Does anyone know what the spray from the CSV should look like?

ctaylor738 · « **Reply #1 on:** July 20, 2016, 13:24:56 »

Update.

After I posted this, I drove the car, let it sit for 15 minutes, and clamped the return line shut. Car started easily. So obviously, some additional pressure helped.

Also verified from receipts in the car that a local dealer installed a fuel pump three years ago.

ja17 · « **Reply #2 on:** July 20, 2016, 13:49:39 »

Hello Chuck, check the inlet fitting of the CSV it has a fine screen in it which is often times clogged or restricted.

ctaylor738 · « **Reply #3 on:** July 20, 2016, 16:29:16 »

Filter is clear. Here is a video of the "squirt." The bench tester is calibrated to the pressure at the CSV in the car.

You'll need to download and rename to .mov to view. Sorry.

Tyler S · « **Reply #4 on:** July 20, 2016, 17:07:32 »

Chuck, Try cracking the throttle slightly so that the fuel charge can be carried down the intake during cranking. With the throttle closed theres not much air flow down the intake path. Its all coming from the idle air screw and down to the runner rail. This is because the wrd airflow is cut off when hot and is where the csv normally gets its air from when cold.

Benz Dr. · « **Reply #5 on:** July 20, 2016, 17:25:55 »

The fuel coming out of the CSV nozzle/s should be very well atomized kind of like a spray can of paint. If it's dribbling out the nozzle/s could be plugged. At .7 bar it should still spray reasonably well.

ctaylor738 · « **Reply #6 on:** July 22, 2016, 00:19:16 »

Tyler - every conceivable starting technique has been tried.

Dan - getting fluid out of both nozzles.

Its looks like a newish CSV. Any idea what would cause this lack of atomization?

Shvegel · « **Reply #7 on:** July 24, 2016, 23:40:56 »

I am guessing that you are dealing with leaky outlet valves on the injector pump. By clamping the return line you are in effect acting performing the function of the outlet valves of the injector pump and are keeping fuel from pushing backwards past the valves. This system is very fussy when it comes to leaks from the injectors or the outlet valves, Every system since ours has had some form of outlet regulator (In addition to an outlet check valve at the electric pump) and fuel accumulator added to the system which allowed for some leakage at the injectors etc so I am guessing they learned a lesson on our cars.

Try removing the clamp just before starting and see what happens.

Tyler S · « **Reply #8 on:** July 25, 2016, 00:08:25 »

Chuck, I watched your video. That looks completely normal to me. Your not going to get atomization like you would a fuel injector because it is only supplied with 12 psi and also it does not have a spray tip like an injector. Its just 2 holes. Its the fuel system equivalent of a windshield washer nozzle. This is one reason this design when away and a proper cold start "injector" was used.

ctaylor738 · « **Reply #9 on:** July 25, 2016, 19:17:50 »

On Gernold's advice, this morning I retested the valve on the car, I recruited a Helper because it's hard for me to fire the valve and watch the spray. I connected the fuel line with the valve turned around from its normal position so it sprayed outward. When I hit it with battery voltage, the Helper (knowledgeable Pagoda owner) reported that the spray was a fine mist from both nozzles. Go figure. It might be the difference between gas and the BG44 I was using on the bench.

Good news is that the car doesn't need a new valve or electric pump. Bad news is, still no explanation for hard warm start.

I should mention that before I messed with the valve, I cleaned and tested the injectors - perfect spray pattern, no leak down. Also adjusted the valves, installed new non-resistor plugs, checked dwell and timing, set idle mixture a little rich. Car is running as good as it gets. No reason that I can see for the hard hot start.

wwheeler · « **Reply #10 on:** July 25, 2016, 20:54:51 »

Just for grins, have you tried disconnecting the start solenoid when starting hot? There is another thread dealing with this very thing. I personally can say it helped my car. Easy to do and will tell you quickly if too much fuel could be the issue. What to do after that is another story.

ctaylor738 · « **Reply #11 on:** July 25, 2016, 21:41:12 »

Last week, after sitting for ten minutes or so, it got in a real snit.

I gave it probably four 10 second cranks with maybe 1/4 pedal. Each separate crank, my Hot Start Solution fired the cold start valve for one second. I finally gave up and pulled a couple of plugs out. They were unfouled and bone dry. So I am reasonably confident that it's a lack of fuel.

Today, I have been experimenting with a) run pump for 5 seconds b) pedal-to-the-metal crank hot starts. Three out of three have been successful, firing after less than a second of cranking.

Shvegel · « **Reply #12 on:** July 26, 2016, 09:14:39 »

Remember that the injection pump fuel gallery doesn't keep any fuel pressure at rest. Only the lines from the injection pump to the injectors do. There is a check valve at the outlet of the electric pump and no check or regulator in the return line(I do remember there may be a check valve or regulator of sorts at the outlet fitting on the latest cars). Even a little leakage from the outlet valves(delivery valves) will cause the fuel lines from the injection pump to the injector to lose pressure and may cause the fuel to vaporize in the lines and push the liquid fuel further away from the injectors. This is what is commonly referred to as vapor lock which would be even more aggravated by any fuel that contains alcohol which is fairly common on the west coast.

This can also be caused by leaking fuel injectors but since you are seeing dry plugs I am guessing the outlet valves are to blame.

I really think you were on to something when you said that the car started fine after leaving the return line clamped. If you shut if off, clamp the return, wait 15 minutes and unclamp it and try to start you will probably know the story.

Shvegel · « **Reply #13 on:** July 26, 2016, 11:13:58 »

Another thing to check is if the fuel is staying in the supply side. Shut it off, wait 15 min and open the line on the supply side of the pump. Even though the pump is recent it doesn't mean the check valve is working correctly. When I taught for BMW "NEW" stood for "Never Ever Worked".

ctaylor738 · « **Reply #14 on:** July 26, 2016, 16:20:39 »

Hmm. Even if the alleged check valve on the output side of the pump failed, wouldn't the system re-pressurize itself as soon as the pump started to run? I have always let the pump run for 5 seconds before cranking.

Another Hmm. Hard to believe that all the check valves on the injection pump would fail at the same time.

I think the hot metal lines were known to produce vapor lock. That's why they put the hot start relay on the 230, and made it available for other cars as a kit. Supposedly the 280 pumps had a venting feature to alleviate this, but the 250s had nothing, and seem to have the worst time with this.

Shvegel · « **Reply #15 on:** July 27, 2016, 22:45:38 »

When the car vapor locks when the supply valves are leaking the fuel boils at the hottest point which would be the injector which is nestled right near the exhaust ports in the head. When it boils at the injector it will push the liquid fuel back up the injector lines leaving a nice pocket of fuel vapor behind. The injection pump is a piston pump so it needs to turn a certain amount of revolutions to displace the vapor and push it out the injectors hence the warm start issue.

You will notice that at no time did I use the word gasoline. Modern fuels are a mixture of all manor of stuff particularly in the great states of California and New York. If I were to go way out on a limb I would guess the car isn't driven much and it was last fueled in the winter when federal and California mandates require higher concentrations of alcohol and other oxygenates which will cause the fuel to boil at an even lower temperature. Higher Octane fuels typically have the lowest boiling points.

ja17 · « **Reply #16 on:** July 28, 2016, 14:28:13 »

Hook up a test light to both the CSV and the injection pump solenoid. Monitor the function at all engine temperatures and compare it to the chart for your starting aids. Deviation from the correct function could be a bad thermo time switch or a starting relay. Check the fuel pressure in the system also during starting. Make sure the CSV is spraying nicely. If no success, the check valves or injectors as suggested can be the culprit. Don't miss the simple fix like low fuel pressure from a clogged fuel filter.

Charles 230SL · « **Reply #17 on:** July 30, 2016, 13:51:10 »

I've got an early R11 pump and after shutdown, the fuel lines between the injection pump and injectors lose pressure after sitting awhile. All 6 injectors are new so I'm confident the check valves on the output side of the pump are leaking down. Can these valves be cleaned and/or replaced without removing the pump? I've noticed that several members modified their injection pump outlet/delivery valves with newer ball and seat valves.. can this mod be done on an old R11 pump?

Cees Klumper · « **Reply #18 on:** July 30, 2016, 16:10:09 »

Related question: where on a '69 can I find the starting relay?

Charles 230SL · « **Reply #19 on:** July 31, 2016, 22:20:18 »

Chuck, I apologize for highjacking the thread to ask about the check/outlet valves.
Regarding your 250SL hot-start problem, upon firing are you noticing initial misfires on any cylinders - possibly indicating leak-down?

I'm having this same (hot start) problem with my R11 pump; when it does fire, I've got a definite misfire on one cylinder till the fuel line has a chance to pump up. I suspect my other five check valves are also leaking to some extent, causing me to crank the starter till they pump up enough to open the corresponding injector.

Shvegel · « **Reply #20 on:** August 04, 2016, 21:45:24 »

Charles,
The outlet valves can be changed in the car but they do require a tool to pull them out after the outlet fitting is removed. You will also require a new plastic seal to put them back in. I made a tool to pull mine and then was gifted the factory tool. I still have the homemade tool it is yours for the asking. I believe that he outlet valves are the same across all models with as you mentioned an early and later Ball and seat design. If I am not mistaken the later design is marked with a groove around the valve.

Homemade tool, factory tool and outlet check valve showing both the groove that denotes ball and seat and the white plastic sealing washer.

wwheeler · « **Reply #21 on:** August 05, 2016, 00:43:56 »

Yes and the Torque is very important as well as the procedure to seat the seal. It is all in BBB. Just for grins, here is the tool I made.

Charles 230SL · « **Reply #22 on:** August 05, 2016, 00:47:27 »

Shvegel, thanks for offering the tool... but where can I get six new seals for the outlet valves? I thought they were NLA.

If i can just get new outlet valves and/or seals I may reconsider sending my pump out for a complete rebuild. thanks for the advice, Charles

ja17 · « **Reply #23 on:** August 05, 2016, 01:22:33 »

Hello Pat,
The early cars had a cone and seat type check valve instead of the ball and spring type.

Cees, the starting relays for a 1969 should be on the fender apron near the brake booster. One is for the enrichment solenoid on the injection pump and the other is for the cold start valve on the intake. An additional relay can be for the de-celleration solenoid on the IP. Are you having starting issues?

Shvegel · « **Reply #24 on:** August 05, 2016, 08:47:01 »

Charles,
From the fine folks at Bosch mobile Tradition. Bosch #F 026 T03 028 is the correct kit for your R11 pump. You get every seal and gasket you can change without recalibrating the pump. Not sure if you can get the kit in the US yet but I ordered mine from Europe.Not sure but I think Amazon UK? If you Google the part number you will find a supplier.

http://www.bosch-automotive-tradition.com/en/internet/automotive_tradition/parts/reproduction/motor/dichtungssaetze/dichtungssaetze___mit_teaser.html

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Author Topic: More cold start valve issues (Read 22517 times)