420 SEL WON'T GO AROUND CORNERS again.
 

Hey guys,
I am back after 2 or 3 posts and no answers. Fuel filter and fuel relay replaced. Slow or fast car stumbles and only restarts after repeated gas pedal apps.
Battery good, grounds good. Pumps run on fuel relay jumper but car still stalls.
How about that check valve at pump outlet? Would L or R turns close same?
Somebody suggested partial alarm system failure i.e mercury switch. Any such in factory system for an 86?
Car runs great..in straight line!
Going nuts!

If the car does have a security system the box for it would be on the passenger side under the carpet. A black box marked "VDO". If its there, unplug it.

From what you describe it must surely be something electrical is being affected by the turning forces....

Please describe the operating conditions in which your problems occur.

Does the stumble occur under cruise, acceleration or deceleration? Does it idle roughly?


I would imagine an anti-theft device wouldn't allow the car to start at all - not just "kill it" at the first turn.

Are you sure you have plenty of gas in the tank? Fuel senders do go bad.

When it dies, how does it die? Does it shudder? Is only the engine affected? Do you lose power to the pump when you turn (a simple magnetic 12V light on the trunk attached to the pump leads will tell you if you're losing voltage)?

Have you tried getting a few friends and bouncing one one side of the car or the other to see if it's simply an intermittant contact with the engine running?

Is there a check valve on the fuel return in the engine bay? I know there's one in the tank, which will kill an engine quick. A simple "blow" test on the return line from the engine should make you hear bubbles in the gas tank - if it puts up even a little resistance, it could be the culprit, but lateral movement shouldn't have an affect.

It would help to know what kind of tools you have to troubleshoot with.

Don't lose faith. Your problem is an interesting one, and I love interesting problems. I am, admittedly, not an MB-only tech, but when you get down to brass tacks, there's only 3 things you need for an engine to run. Air, fuel & ignition.

Does it matter how fast you take a corner? Have you tried turning at different speeds? 5mph, 10mph, 20mph, etc...

From what you describe, I'm kind of with the pawoSD - this sounds like a a contact made by inertial forces. It could just be 2 wires rubbing together. Regardless of make, I've come across tons of bad wiring that cause the strangest symptoms...

Does it happen when you turn in either direction? Are there wires anywhere near your engine mounts? Relays usually have make or break contacts which travel in one direction, so if it dies in both directions, that is indeed interesting.

Reply to Jenkins re MB & Corners
 

Hello and thanks for your interest,
Yes it happens in both directions, and that eliminates a lot of your suggestions but don't give up on me.
Fast or slow, yes inertia caused I agree but what. Just for kicks, it doesn't do it all the time...wonderful or is that wunderbar?
When it dies it just stumbles and stops unless I goose the gas, after the turn is complete Fuel. fuel. fuel?
I have filled the tank and placed dry gas in it, no change.
The only check valve that I know of is in the outlet of each(?) pump
Stopping in both directions kinda kills all of these.....don't it?
Nuts!

Stumbling usually indicates a lack of gas. See my fuel pump test above.

I think I sent you an e-mail.

I did, I did send you an e-mail.

Wiggle every wire you can see under the hood while the engine is idling!! If the engine stumbles or dies...you've found the problem area...

At this point, I think I'd try a jumper in place of the fuel pump relay (pins 7&8??), then go drive the car. That would eliminate most of the electrical concerns. If it still stumbles while driving, then put a voltmeter on the fuel pump power leads (use a long piece of speaker wire) to watch voltage AT the pumps while driving.

Double check positive battery cable , the small terminal can be loose, but most likey as stated you have a loose wire,or bad f/p, test pumps individually, 1 could be going out, when the car goes around corners maybe its cutting off, you need f/p gauge to isolate

Hey guys:
My fuel pumps are drawing 32 amps! Wow Arn't they supposed to draw about 10?

Sorry guys. Forgot how to read my own meter. The pumps only draw 4.5 amps!

Next step is to drive it with a fuel pressure gauge connected & taped to the windshield while turning a corner.

You have to rule out one system at a time if you hope to fix the problem.

x2, ive had this happen to me with plug wires. i went around a corner, and the wire grounded out.