Hot starting remedy?

[gnj588d]

Has anyone Fitted a one second time switch to the cold start device to aid hot starting,whats it like to fit and does it work any views    Many thanks Mike Rutledge

[Shvegel]

It shouldn't be too difficult just be carefull when you are wiring the timer. The cold start switch recieves power and activates a ground for the cold start valve. What you are looking to do is supply a ground to the cold start valve.

I actually cured my problem by adding a fuel pressure regulator in the return line from the injection pump. I think there is a check valve in the supply side(My non stock bosch supply pump has one in the outlet) and by adding a regulator in the return from the injection pump it keeps fuel pressure in the pump when the car is shut off.

Unfortunatly my car is apart and I am working out of town so I can't show you any pictures but basically what I did was what Bosch did in later injection systems. I have been running it this way for 5 years and it works well.

[Cees Klumper]

Hello Shvegel - that fuel pressure regulator in the return line sounds like it might just be the solution for my warm start issue as well - where can I find one of those, what 'value' should it have and are there any negative sides to this option?

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[Shvegel]

Cess,
I used a 2.5 bar regulator from a 1987 Saab 900. If I remember correctly you will also need the bracket it mounts on, the big nut that holds it to the bracket and the hose that connects the regulator and the fuel rail.

I seem to recall that the fuel return hose off the injection pump was plumbed into the regulator inlet(the threaded flare fitting) using the unmodified original fuel hose which was swapped end for end and the return(barbed fitting) was connected using a new piece of hose and one of the fittings off the Saab line. the regulator was then mounted on the side of the pump using one of the side cover screws to retain the bracket.

I will try and get a picture of the install from my bodyman.

You need to make sure there is a reliable check valve at the pump. I believe there is an inlet check valve on the injection pump.

The way the stock system is supposed to work is that the residual fuel pressure(after the car is shut off) is supposed to be held by the check valves at the outlet tubes of the injection pump and by the pop off valve in the injectors which keeps the fuel under pressure in the lines where it resists vaporizing due to the heat soak from the stopped engine.

Unfortunately there is no accumulator or reservoir for the fuel. If there is anything less than a perfect seal the pressure drops rapidly and the fuel in the injectors begins to vaporize(vapor lock) which forces the liquid fuel even further back down the fuel lines from the injectors. When you go to start the car hot you have no fuel in the injectors only vapor.

In later systems(the CIS or constant Injection System and the LH electronic system) Bosch corrected this by eliminating the check valves at the outlet of the fuel distributor and keeping the entire system under pressure using a regulator which has a rubber diaphragm and stores a small quantity of fuel under pressure. This eliminated the need for a perfect seal at the injectors. Even if there is a tiny leak enough fuel was stored under pressure to maintain residual pressure at the injectors and prevent vapor lock. Bosch also mounted the fuel filter on its side to trap some air under pressure and act as a reservoir as well but this doesn't seem to be necessary on the 113.

OK now for the drawbacks:

The first problem may be that your original electric fuel pump may not like the pressure(I am currently running one from a Saab 900 although which model escapes me at the moment). I have never put a gauge downstream of a stock electric pump running in a stock system and although there is a restriction in the return fitting of the injection pump it may not run anywhere near the 2.5 bar of the regulator. I would test it running stock and with the return line pinched off to see what the pressures are.

Also the injection pump is held under pressure in the plungers so there is a chance of fuel leaking into the oil past the plungers of the injection pump. There are no seals on the plungers and they rely on incredibly tight tolerences to seal properly. I was of the belief that if they could withstand the injection pressure they would be fine at 2.5 bar and this has proven to be true although I did check my oil level quite a bit after the modification.

As a sidenote I would swear that my engine seemed to run smoother after this modification. I attribute this to lack of reversion in the fuel system and a more consistent fuel charge.

As I stated in my previous post I have been running it this way for 5 years and at least 10,000 miles without a problem.

I am probably going to be in the Netherlands up near Dorp in a few weeks(the man I work for is building a new yacht at Feadship Royal Van Lent on Kaag island) If you need anything from the states let me know.

[gnj588d]

Has anyone tried the MB kit part no.001 545 16 24{switch}and 108 540 10 09{harness}it seems more straight forward. Cheers Mike Rutledge.

[n/a]

gnj588d

This topic has been addressed several times on this and other web sites.  The scenario seems to go something like this.  The engine will start well cold and will start up again easily right after the engine is cut off.  However, when the car sits for a while, it is hard to restart.  I believe the cause has been addressed already.  

The simplest and surest solution for this is to install a switch to manually activate the solenoid on the csv.  Either a push button switch or a spring loaded toggle switch  will do the job.  Both os these switches are normally off and will activate the solenoid only when the switch is "held" in the on position.  The switch is there to be used on an as needed basis.  You can play around with thermotime switches, time delay switches and any number of other remedies, but this will give a surer fix than any of the other fixes.  It may not be exactly original but it sure is effective.    

To wire up the switch, run a wire from a fused circuit to the switch and then another wire from the switch to the csv solenoid.  Hide the switch in some inconspicious place under the dash.  You can use the switch when you need it inject a little extra fuel into the intake manifold or ignore it if you do not need it.  It is worth the peace of mind to know you will never again need to be in a crowd of people with a car that does not start as it should.

Good luck

Iverson

[glennard]

A thought on 'starting woes'.  If the engine isn't properly idleling(at 750(approx) rpm, minimum fuel, enough air to maximize rpm for the minimum fuel, but enriched 50 rpm), then it will be hard to start.  All the compensations(altitude, temp, etc.) are based upon the correct idle settings.   Higher rpms at road speeds are determined by the mechanical relationship of the rotation of the FI plungers(rack) and the opening of the butterfly.  This relation is documented by the angle tables in the MB BBB, etc.

[graphic66]

The manual shows to hold the throttle about half when the engine is warm. This helped my warm starting. The temp gauge works all the time, if the engine shows any temp I just give it a little throttle and it starts right up. There is a lot of useful info in the owners manual.

[Cees Klumper]

Thanks much for the reply Shvegel - very impressive! All the ammunition I need to see if this will cure my warm starting problem.

I make it over to the US reasonably often, will be in New York again in early November and after that will be 'on tour' all around, so thanks for your offer but I can take things home that are handy to have (such as Intuit's Quicken software, or many a Sears Craftsman tool) pretty easily myself.

Thanks again,

quote:Originally posted by Shvegel

Cess,
I used a 2.5 bar regulator from a 1987 Saab 900. If I remember correctly you will also need the bracket it mounts on, the big nut that holds it to the bracket and the hose that connects the regulator and the fuel rail.

I seem to recall that the fuel return hose off the injection pump was plumbed into the regulator inlet(the threaded flare fitting) using the unmodified original fuel hose which was swapped end for end and the return(barbed fitting) was connected using a new piece of hose and one of the fittings off the Saab line. the regulator was then mounted on the side of the pump using one of the side cover screws to retain the bracket.

I will try and get a picture of the install from my bodyman.

You need to make sure there is a reliable check valve at the pump. I believe there is an inlet check valve on the injection pump.

The way the stock system is supposed to work is that the residual fuel pressure(after the car is shut off) is supposed to be held by the check valves at the outlet tubes of the injection pump and by the pop off valve in the injectors which keeps the fuel under pressure in the lines where it resists vaporizing due to the heat soak from the stopped engine.

Unfortunately there is no accumulator or reservoir for the fuel. If there is anything less than a perfect seal the pressure drops rapidly and the fuel in the injectors begins to vaporize(vapor lock) which forces the liquid fuel even further back down the fuel lines from the injectors. When you go to start the car hot you have no fuel in the injectors only vapor.

In later systems(the CIS or constant Injection System and the LH electronic system) Bosch corrected this by eliminating the check valves at the outlet of the fuel distributor and keeping the entire system under pressure using a regulator which has a rubber diaphragm and stores a small quantity of fuel under pressure. This eliminated the need for a perfect seal at the injectors. Even if there is a tiny leak enough fuel was stored under pressure to maintain residual pressure at the injectors and prevent vapor lock. Bosch also mounted the fuel filter on its side to trap some air under pressure and act as a reservoir as well but this doesn't seem to be necessary on the 113.

OK now for the drawbacks:

The first problem may be that your original electric fuel pump may not like the pressure(I am currently running one from a Saab 900 although which model escapes me at the moment). I have never put a gauge downstream of a stock electric pump running in a stock system and although there is a restriction in the return fitting of the injection pump it may not run anywhere near the 2.5 bar of the regulator. I would test it running stock and with the return line pinched off to see what the pressures are.

Also the injection pump is held under pressure in the plungers so there is a chance of fuel leaking into the oil past the plungers of the injection pump. There are no seals on the plungers and they rely on incredibly tight tolerences to seal properly. I was of the belief that if they could withstand the injection pressure they would be fine at 2.5 bar and this has proven to be true although I did check my oil level quite a bit after the modification.

As a sidenote I would swear that my engine seemed to run smoother after this modification. I attribute this to lack of reversion in the fuel system and a more consistent fuel charge.

As I stated in my previous post I have been running it this way for 5 years and at least 10,000 miles without a problem.

I am probably going to be in the Netherlands up near Dorp in a few weeks(the man I work for is building a new yacht at Feadship Royal Van Lent on Kaag island) If you need anything from the states let me know.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic