weird starting problem
 

Hi Guys

I have a weird starting problem.
Usually, the car starts without any problems on a first short starter. Sometimes it takes a little longer starter but it starts without any problem.
However, if for any reason it didnt start on the first starter (long or short) it will not start for 10-15 minutes unless I press the gas pedal all the way to the floor and hit the starter for about 10 seconds.

Now, this usually means that the engine is flooded...but how can it be? :confused:
I mean, the CO is normal, fuel pressure is normal so how can it get flooded?
Is it possible that too much fuel flowing to the engine while it is in idle? if so then I should see it in high CO readings right? :confused:

What can I do to solve this problem?

Thanks for your help!

check the fuel injectors for leaks try adding some techron to the fuel

Everything in the injectors area is clean. no visible leaks.
Why do you think Techron might help?

I think the Techron mrmerlin is referring to is the concentrated fuel system cleaner. I've used it myself... with good results.
-Kerry :)

Related subject, are the inlet strainers removeable from the Bosch electronic injectors without damaging them? How?

Yes, but how fuel system cleanup can solve flooded engine issue? or you think that it can be related to block injectors?

Yoni, you have electronic injection, right?

And a hard start problem?

On a cold hard-start problem, as temperatures drop, the thermo-time switch could be the issue.
Its a common source.

The thermo-time switch is used to regulate the cold start injector and limit the amount of fuel on a start. If its bad, it acts like its flooded. The switch on my 4.7 84 cars is located on the passenger side of the front of the engine. It looks like a temp sensor. Its top faces the front of the car, and it screws in towards the back of the car. I've replaced them on two USA 4.7 cars.

Fixed the issue on both.

Well, I have mechanical injection...its a 80' model. is your solution still relevant?
How can I test the cold start injector to check if it is ok?

I don't think so. Thought that the 80 EuroS was electronic fuel injection. Sorry.

(No experience with mechanical injection / there are control pressures and mechanical warm up regulator, apparently.)

Yani,

I am not that clear with the specifics (your descriptions) of the issue...but a euro CIS could have a Fuel Accumulator that is failing, not retaining pressure for second or warm starting.

I am not sure if the WUR (warm up regulator) is a cause??

Jon

I thought about the Fuel Accumulator but I am not sure that it is the cause since when I start it with gas pedal pressed to the floor, it starts after 10 seconds and the engine feels flooded...I know that the Fuel Accumaltor is hard thing to test...
Could it really be the problem ??

Static Pressure Test -
 

Hey Yoni, It sounds like your static fuel pressure is bleeding down after the car has been parked for a while. The CIS mechanical injection system should hold a fixed supply of static fuel pressure in preparation to restart the engine between a check valve screwed into the fuel pump and a parallel circuit that includes the fuel accumulator, a cold start injector and the 8 cylinder intake injectors. Your symptoms may indicate that one of these components is allowing the static pressure to slowly bleed off at engine shut down. Check the static fuel pressure after the car has sat for a while.

As a temporarily fix, you can jumper your fuel pump relay (pins 30 and 87) to provide power directly to the pump which will reestablish the needed pressure and easily allow you to restart your engine. The procedure you are currently using (holding the accelerator to the floor) will flood the engine every time.

One other comment - If the static pressure is bleeding off at the fuel pump - some of the early pumps integrated the check valve into the output port of the fuel pump. You may have to replace the fuel pump with a later year model that has a replaceable check valve. (I have seen where some owners with the early style fuel pump have added a new Bosch check valve (stacked in series) onto the built in check valve output port)

Good Luck, Michael :)

Hi Michael,

Thanks for your explanation!
But, if I understood correctly then if I am loosing static pressure, my FIRST start should be always very difficult. but in my case, the first start is usually good. if for example I try to start it at the first time and from some reason I stop the starter before it started and try again, then it is almost impossible to start.

Or, maybe the pressure issue is not stable...so some time it holds pressure and some times it doesnt and then I get this affect...strange...:confused:

Forgot to ask...is it possible that the fuel pump pumping too much fuel when starting the engine? then it can explain the flooding issue...

The pump has a max flow rate and usually will not exceed it...bad/low/no pressure will cause a hard second/warm start. If so, it is most likely the accumulator or could be the check valve leaking. Cold start is usually indicated by other symptoms.

Look inside the right rear in-fender panel at the accumulator, if it has a gas smell and you can see seepage on it, it's leaking gas and pressure. Look (under the pump panel) at the check valve, either within the pump or external for any leaking/seepage.

Jon

Thanks! will do!

Static Pressure - Test
 

Hey Yoni, First use a gauge to test for the required static pressure. This will immediately indicate if this is your problem. A loss of static pressure is usually TIME related. The longer the car is parked (the increased loss of static pressure) and the more difficult it will be to start.....

There is a check list in the maintenance manual that gives the acceptable range of static pressure vs the length of time the vehicle sits. If I remember correctly your static pressure must not fall below the 14 - 15 psi mark or restart issues will occur.

Good Luck, Michael :)

if the fuel is dirty,
adding some Techron may clean the fuel components out.
This is the easiest thing to do..


If the accumulator is original replace it, ( in the RR wheel well)
also consider replacing the check valve in the fuel pump,
if it has a replaceable valve

Cold Start Injector -
 

Hey Yoni - Don't forget that during the initial start your engine is cold and the cold start thermistor switch (in the front water jacket) is probably energizing your cold start injector as the starter turns. This solenoid style injector throws any remaining residual fuel pressure left in your system into the intake manifold (like a bucket with a hole in the bottom) and helps to start any engine as long as there is at least some residual pressure remaining. If your car does not start after the 1st cold engine attempt - all of the residual pressure may have been used up. Any additional attempt has no residual fuel available. Once the engine has warmed up - the cold start injector is no longer in the start mix.

After driving around a while - everything will be fine until you park the car. Then if you start it back up within a relatively short period of time, your residual pressure may not have bled down very much. But if you have shut down the car for too long, the residual pressure may now be too low for an easy start.

At this point the engine is probably too warm for the cold start circuit to activate and since the 8 primary intake injectors only open by pressure, they wont even begin firing until about 30 Psi is in the lines. The fuel pump has an air flow safety switch in the mixture control unit which doesn’t allow the fuel pump to run until air is being drawn into the intake from piston movement. Naturally - if the residual fuel pressure is too low - it takes 10 - 15 seconds of starter operation to bring the fuel pressure up high enough to begin opening the main 8 intake injectors.

All the above information is assuming that you have tested for a residual pressure issue. Please realize that we are all troubleshooting by guess and by golly using the information provided and there may very well be a different problem you need to chase down ... check Mrmerlin's input.

Hey Landseer - the thermo-switch (cold start thermister switch) may be a good call if the cold start injector is trying to over fuel every start process. Yoni - check to see if 12 volts is being applied to the cold start injector at every attempt to start your car.

Good Luck, Michael

So it does have a thermo-time switch? I'd certainly replace it.

I have the exact same issue with my CIS. It's probably not flooding, it just feels like it. It is most likely loosing pressure as everyone says. Most likely accumulator. (my theory) When the pressure drops the heat makes air bubbles in the fuel lines that purge out and make it stumble (like it's flooded) That's why no smoke or rich smell is noticed, it's not flooded. Also I noticed that the type of gas I use has an effect. I used to use Mobil and it always happened. I switched to Shell and it never happens any more. The only time I will have issue's is that first tank in the spring that is old and stabilized. Once I go through that tank it's perfect.

Well, I guess that I will start from the accumulator. Although in my case, I do have a strong smell of fuel after I start it with the gas pedal pressed to the floor :\

Thanks Michael! ;)

Troubleshooting Steps -
 

Hey Yoni, Even under the best of circumstances most experienced owners will readily confirm that it can be expensive to maintain a 928 - but to just start swapping out parts without taking steps to troubleshoot a problem can get real pricey very fast.

It is not that your planned attempt to change out the accumulator might solve your problem - it is just that this part can be easily tested. The accumulator is simply a sealed canister containing a spring on top of a flexible rubber bladder. As the bottom inlet is exposed to your operating fuel pressure the spring is compressed. It holds this position until the engine is shut off. With the fuel pump now stopped - the fuel pump check valve on the back end of the main fuel line and the injectors at the front end of the main fuel line are supposed to now seal the system. The accumulator spring (basically plumbed between the fuel pump and the injectors) now expands to hold a minimum of 14 Psi within the fuel lines - waiting for the next engine restart.

Once the accumulator is removed - it is simple to test. Apply about 25 psi to the bottom inlet port using an air nozzle. This will compress the spring. No air should pass out of the top connection. When the air nozzle is removed, the spring will extend and push the air out.

You should not have to step on the accelerator to restart a cold or warm engine.

Good Luck, Michael :)

Jk's right. Test as much as you can first. Since you do have the gas smell I assume you are getting plenty of gas , maybe too much. A failed accumulator would most likely not create that. I would look towards a leaky cold start valve and/or the components that control it.

hmm.. seems like my car problem.. Will read it later..

Well, found the problem...
amazingly it was a battery problem!!! it seems that it has some sort of internal malfunction.
So thats why from time to time it didnt have enough power! it did have enough power to turn the starter but not enough for all other electrical systems...
I just replaced the battery and the car starts immediately at any time :)

I am sooo happy!

Excellent!
Sorry to lead you all over the place.
Michael had the voltage thing pegged, though, didn't he?

Congrats!

indeed! :)
thanks!

Keep in mind that your CIS fuel pump has a higher flow rate and produces more pressure than the ones used later in the electronic injection systems.

More-Better Capacity
 

Naturally, it is important to only install a fuel pump that is capable of producing the correct operating pressure and flow rate - this is especially true for a high performance vehicle. During the troubleshooting phase of this post, I had only mentioned to Yoni that he may have to update his fuel pump if he had the earlier design (with the internal snout check valve) and the check valve was defective. Some 928 owners install a newer style pump not only for the replaceable check valve but for the ability to install a larger pump with more-better operating capacity.

Michael :)