85 3.2 no start

[benzboy]

hey all. I just tried starting my 3.2 a few day ago. it wont start. I cranks over fine, but no start. I had it out for a nice run a few weeks back. I though possibly it might be the dme. I changed it out with my spare. but no luck. I had an extra coil. so I tried that and nothing. it had a full tune up a few years back. im thinking possibly it could be the fuel pump. are they located up by the tank? and yes I have gas in the tank. does the fuel pump hum when the key is turned on to the on position? im not sure where to begin. I don't want to start replacing parts without knowing what is causing the problem.

[r_towle]

Fuel Pump Relay?
It controls both fuel and spark.

Little black relay under the seat.

Search here for how to hotwire that relay for testing before you buy something you do not need.
I have two at all times, one in the glove box with a 10mm wrench to take it out..

Seems to be a flaky part.

[benzboy]

that's the dme relay right? I did switch it out, and nothing

[DRACO A5OG]

Do you smell unburnt fuel at the tail pipe?

You do not have a round relay under your driver seat.

[gtc]

Here are some things that I checked when going through my no-start:
1. Measure reference and speed sender resistance - Should measure ~960 ohms.
2. Check fuel pump by jumpering pins 30 & 87B on the DME relay socket.
3. Measure Coil resistance: Side to side, side to top (see Bentley Manual for specs)
4. Measure Cap and rotor resistance (see Bentley)
5. Measure Plug wire resistance (3k ohms)
6. DME relay should click when cranking
7. ICV should hum/vibrate with ignition on.
8. Check/clean grounds at battery and on intake manifold.
9. Measure CHT sensor resistance (see Bentley)

What Ingo Schmitz had me try, which finally indicated that the DME was dead (the ECU, not just the DME relay) was to measure resistance between pin 1 and 6 on the DME box. Mine had zero resistance in both directions, which somehow told Ingo that it was fried.

The fuel pump does not run with the engine off, which is why you need to use a jumper. It is hard to hear the pump when the engine is cranking, but you can hear it easily when you jumper it.

[benzboy]

well I just checked the dme relay. it clicks when it cranks over. im leaning towards the fuel pump. is there markings on the dme socket, so I know which ones to jump to test the fuel pump?

[kidrock]

the first thing I would do is check for both fuel and spark at the engine. Anything before that (except for switching the DME relay) is like a dog chasing its tail.

[DRACO A5OG]

Do you smell fuel, if so, it isn't your pump.


+1 check the ohms on ref + speed sensor

[benzboy]

I don't smell fuel out the exhaust. where is the pump located? on my 73 its by the rear driverside tire. are the carreras up front by the tank?

[rusnak]

Try spraying a bit of starting fluid into the intake, upstream of the paper filter element. If you have a remote starter switch, then you can spray while it's cranking over (better) or recruit a helper.

[DRACO A5OG]

Originally Posted by benzboy

I don't smell fuel out the exhaust. where is the pump located? on my 73 its by the rear driverside tire. are the carreras up front by the tank?

Okay, it is under neath the stone guard right behind the fuel tank if your stone guard is missing.

[Quicksilver]

The fuel pump doesn't turn on with the key. The DME triggers the DME relay when it sees that the engine is turning. That is why jumpering the relay will run the fuel pump.

[benzboy]

would someone show me how to jump the dme relay plug to activate the fuel pump. thanks

[kidrock]

I don't have immediate access to the plug numbers at this moment. Hopefully somebody will chime in.

But I wanted to remind you that the pump can still "whirr" and not provide fuel. I would follow Rusnak's advice first, personally.

[benzboy]

just a quick update on the no start problem. car still isn't starting. I did try the staring fluid and nothing. its not the dme relay or coil either. imeaning towards toe cht sensor. if its the cht sensor. should I still smell fuel from the exhaust??

[ynotony1966]

I have the same problem with my 85 today. let a friend drive it and he stalled it 3 times getting going and on the fourth time no start no gas smell

[DRACO A5OG]

Oh geez, Friends don't let Friends drive their 911 :-o

Benz & Ynot, track down a pelican with a 3.2 and see if you can borrow their DME ( not relay but the ECU ) and try to start her. Remember their DME into your cars.

Jim

[ynotony1966]

it started. something is going out? happend the other day too. if i put my ear up to the enrichment adj area i can hera a humm even with the key off

[benzboy]

I have a spare dme relay and switched them out. and nothing. today I pulled a wire put a spare plug in the wire, had a friend tun the car over and I grounded the wire. I had no spark. so what could be the reason here.

[DRACO A5OG]

Not the DME Relay but the actual ECU DME, I am certain there is a fellow Pelican 3.2 in the area.