190e 2.3 starts than stalls after 4 seconds

[digdig]

I recently rebuilt the motor and after reinstalling, the engine won't remain running. It seems that it is running out of fuel. the fuel pump is good and it seems that all electrical connections are good. there is enough pressure at the regulator and fuel is present at the injectors. It seems like the computer is killing fuel after a few seconds. HELP I'm losing my mind over this. thanks for any help. :cry:

 

[Malcolm Brown]

Can't help with the specifics, but it is worth checking whether the fuel pump is operating for the 4 seconds the engine is running. The pump runs briefly to pressurise the system when the ignition is turned on and that might be enough to run the engine for a few seconds. Get someone to have a listen to it while you go through start-up.

 

[digdig]

fuel pump

after a little more exploring , I think the problem may be the fuel relay. I read in another forum of a similar problem. I would like to jump the pins on the relay but am not sure of how exactly to do this . Any help would be appreciated. Thanks

 

[joe bloggs]

Connect 30 & 86 (opposite each other, check pin numbers on relay) but be very careful as pin 30 is not fused, repeat not fused, this should only be done to isolate the fault and under no circumstances should the car be driven this way.

 

[joe bloggs]

Correction, Pins 30 & 87, same caution applies

 

[digdig]

Thanks jo the car ignited and I should be getting a nice insurance check any time now. Just kidding. I ordered a new relay and am waiting patiently to try it out. Thanks again for the help. I'll let you know how I make out.

 

[digdig]

fuel pump

Well the new relay came but didn't cure the problem. After jumping the pins on the old relay I tried to set the timing. I can turn the distributor and nothin changes. I also noticed that my tach isn't working. What am I doing wrong? What other ideas do any of you have? I also need a better shop manual than the haynes book I have , where might I find one? Thanks again for any help forthcoming

 

[joe bloggs]

As the tach and the f.p.relay need a "td" ignition signal to operate, this has to be the problem area, check the small screw connector next to the diagnostic socket, this is where the td signal comes from the ignition module and connects to the tach/f.p.relay/jetronic, as the car runs with the fpr bridged out, the tdc signal from the distributior (thick green cable) must be present and connected to the ignition module. I dread to say but it could possibly be the ignition module as it takes the signal from the distributor and 1. fires the coil 2. sends an amplified version out to the tach/fpr/jetronic, its this bit that could be missing.
Try disconnecting the wires at the small screw mentioned earlier and reconnect only the wire from the ign module to the wire from the fpr (missing out the tach - which have been known to short out the td signal- and the jetronic) you may have to use a test meter between the fpr socket td connection (look at underside of relay for pin location) and the wires at the small screw connector. The other wire from the ignition module should be easy to identify (I think these wires are all either green/yellow or green/white)
Also make sure ignition module earth is connected (under coil mounting bolt)
It is always possible that the cable from the distributor is damaged and providing a very weak signal (just enough to fire the coil and no more) or the distributor also could have a poor output, check with ohmeter while wiggling the cable.
The reason the fpr needs this signal - and the reason the car only runs for a few seconds - is that when ignition on the fpr runs for 1-2 seconds, when you crank the engine the relay also runs (while cranking) and when/if the engine fires the td signal should take over to keep the fpr operating and the engine running, idea is if the engine stops the fuel stops.
Keep me posted

 

[joe bloggs]

Just had another thought, your car may use a flywheel pickup to tell the ignition module where tdc is, has this been refitted correctly (thick grey cable - may have black sleeving over it, goes into block near gearbox) check with ohmeter, unlikely - as engine runs - but worth a look (if it applies to your car) do the other stuff first

 

[digdig]

I checked it today joe. I also noticed in the haynes book that all the functions that are screwed are also tied to the overvoltage relay. Is there any way to check this? If so . How? I didn't take the car apart. so It's twice as hard to fix it. It was however all working up until the head gasket went. then it sat awhile and here we are. I just want to drive it again.

 

[digdig]

I checked all connections so they all seem good. there are three relays behind the battery. One is the fuel pump the other with the fuse, I assume, is the voltage relay but what is the other one? I checked resistance on the td wire freom the ign module to the relay and it's good. how can I check the ign modul itself?

 

[digdig]

One other thing My check engine light is on, probably related to the problem . Can I check an engine code and if so how do I do this? Thanks

 

[joe bloggs]

Check Engine Lamp?? on a 190, never seen one, where is it on your car??.
Cant be the Voltage relay, the td does,nt go there, and as far as I know the ign.module does'nt get its supply from the over voltage relay (need to check diagram). As car runs with fpr bridged (with no tach) the td signal has to be either missing, as it leaves the ign. module, or shorting out somewhere (tacho???) Best way is to disconnect tacho at diagnostic plug, if you can establish that the td is missing then its a new ign. module. ££££££. double check everything first.

 

[digdig]

O.K. Joe you definitely have it right. The problem I have is that the wiring schematic I have is out of a 1988 haynes manual. The diagnostic td screw only has 1 wire on it. It shows 8.5 volts while running and fluctuates in a steady rythem. I have 0 at the fpr td pin and don't know how to test at the ign module. I pulled back the wiring cover to expose the wires and tested the big green wire but got 0 volts. The car also runs with the ign module disconnected to my suprise. We're narrowing down the problem but I need help to test everything correctly. After this I might have to go get a job at mercedes (ha ha ). Thanks again