3.0 hiccuping to not starting CDI?

[Hetheca]

Recently purchased a '74 targa with a 3.0 engine. I'm in OC, CA

Running fantastic the past few weeks.
A week ago driving, car went dead. Pulled over and started right up.

A few days later on the freeway small hiccups while driving. Once every 60 miles maybe.

Drove yesterday fine and parked for a couple hours. Car wouldn't start after but finally started and was able to drive 2 miles home from where I was. Acted like a car with really bad Carbs. Backfired on the way home.

After reading threads last night I checked the multi purpose relay in the front..it very was loose so I pushed it in and then tried to start the car. It fired up right away with no issue.

Today, Nothing. Won't start. Tries really hard and fires then stops.

Key in on position, Fuel Pump runs. It's not supposed to I know so maybe the wiring when the 3.0 was installed? Battery really strong. Lights on dash work fine, stereo etc fine.

Cleaned the prongs on the FP Relay just in case.

Has a Black Bosch Germany Coil. Has a Bosch CDI 227300

I know there are many out there with similar issues and maybe a good post I'm not finding. Can I check the CDI somehow or should I take in to a local shop to test?

I don't have the right socket size to check for Spark right now but I'll plan to tomorrow.

Any other help much appreciated.

[timmy2]

Nice looking car.
The ‘74 will allow the fuel pump to run with ignition on, safety cut off didn’t start until ‘76.
(Unless they re-wired the entire car to install the 3.0, which is doubtful)
Test for spark is the first step. Especially if it fails when hot.
Spread the pins on the fuel pump relay with a razor blade is second.
Then check for a pop off valve in the air box under the air filter that may be open or dislodged.
Many more detailed tests to do if these simple checks don’t find anything.
(Fuel pressure system checks, check for electrical and grounding issues etc)
Do the simple tests first and report back.

[Bill Douglas]

As you and Denis mentioned; the fuel pump relay. Maybe clean the bit where it plugs into with contact cleaner and something to give it a scrub out. I use a small rat tail file set that is handy for this sort of thing. And of course give the relay itself a clean.

Good luck, the car and engine look great so I'm sure it's something minor, but what LOL

[Hetheca]

Have checked the pop valve in the air cleaner a few times.closed and opens fine. Will try and spread the FP relay pins a bit, and clean the female end. Checking for spark tomorrow too.
Will follow up after the above.

[Mixed76]

Also check your grounds at the battery and engine. My 76 3.0 would crank and crank but not start till I fixed a loose battery cable.

[wgirardot]

Originally Posted by Hetheca

Recently purchased a '74 targa with a 3.0 engine. I'm in OC, CA

Running fantastic the past few weeks.
A week ago driving, car went dead. Pulled over and started right up.

A few days later on the freeway small hiccups while driving. Once every 60 miles maybe.

Drove yesterday fine and parked for a couple hours. Car wouldn't start after but finally started and was able to drive 2 miles home from where I was. Acted like a car with really bad Carbs. Backfired on the way home.

After reading threads last night I checked the multi purpose relay in the front..it very was loose so I pushed it in and then tried to start the car. It fired up right away with no issue.

Today, Nothing. Won't start. Tries really hard and fires then stops.

Key in on position, Fuel Pump runs. It's not supposed to I know so maybe the wiring when the 3.0 was installed? Battery really strong. Lights on dash work fine, stereo etc fine.

Cleaned the prongs on the FP Relay just in case.

Has a Black Bosch Germany Coil. Has a Bosch CDI 227300

I know there are many out there with similar issues and maybe a good post I'm not finding. Can I check the CDI somehow or should I take in to a local shop to test?

I don't have the right socket size to check for Spark right now but I'll plan to tomorrow.

Any other help much appreciated.

A few easy steps to make: check that fuse 16 is good and clean. Re-seat the 2 big connectors in the engine bay. Make sure igintion wires are seated properly.

Bill

[997at]

I do think it's a good idea to check some of the basics first as have been suggested.....that being said I'm putting a bet on the issue being either the CDI or the coil. Classic symptoms.

[pampadori]

I agree, my money is on CDI.

[timmy2]

What year is the 3.0? Just curious, as after ‘79 Porsche started adding more emission crap to to the US engines that can cause more problems...

[Ian Comerford]

In the picture of your engine bay on the left is a panel with a red relay. To the rear of that panel near the engine mount is a multi pin connector. Disconnect this and try tightening the female parts. Mine had a similar issue and it turned out to be this plug/socket combo not connecting very well.

[Paulporsche]

Are you still running points? If so, check the gap/dwell. Check ignition components before fuel injection.
As others have said, spread the red relay contacts and check the electrical connections there, incl the fusebox.

[Hetheca]

Think I've narrowed it down.

1. Cleaned FP relay pins and spread then very slightly, cleaned female end as well.
2. Reseat multi pin connector in engine bay near FP Relay.
3. Pulled plug to check spark, Fouled so pulled all plugs and all needed replaced. Replaced all.
4. Still no start. It tried and backfired.
5. Realize I'm not hearing the Fuel Pump but instead a motorized Antenna that's not connected to the antenna. Passenger side front fender
6. Also realize I was hearing 2 "pump like" noises before the car stopped working. The 2nd noise from center forward behind firewall. And now I understand that this is not an in tank FP but In line under the the front floor pan.

- Could still be the FP Relay
- Could be the FP
- Don't think it's the CDI

You guys run 89 or 91 gas?

Thanks for all of your impute, greatly appreciated.

[Hetheca]

Engine is a '79 @timmy2

[boyt911sc]

Originally Posted by Hetheca

Think I've narrowed it down.

1. Cleaned FP relay pins and spread then very slightly, cleaned female end as well.
2. Reseat multi pin connector in engine bay near FP Relay.
3. Pulled plug to check spark, Fouled so pulled all plugs and all needed replaced. Replaced all.
4. Still no start. It tried and backfired.
5. Realize I'm not hearing the Fuel Pump but instead a motorized Antenna that's not connected to the antenna. Passenger side front fender
6. Also realize I was hearing 2 "pump like" noises before the car stopped working. The 2nd noise from center forward behind firewall. And now I understand that this is not an in tank FP but In line under the the front floor pan.

- Could still be the FP Relay
- Could be the FP
- Don't think it's the CDI

You guys run 89 or 91 gas?

Thanks for all of your impute, greatly appreciated.

Hetheca,

I have been following your troubleshooting from the very beginning when you proclaimed the CDI failed. It is easy and simple to verify if the CDI is the culprit. Hook up an inductive timing light and crank the engine. If the CDI is defective, you would not get an ignition signal. Another test is to test the CDI on a running engine or install a good known CDI in your engine.

If I were in your shoes, I would do the following:
a). Install a CIS pressure gauge kit and measure the fuel pressures (CCP, WCP, SP, & RP). The pressure readings will tell you more about the condition of the FP.
b). Pressurize the airbox and intake runners to locate sources of unmetered air.

And I will bet my money that you have a significant vacuum leak causing the mixture to get too lean to start. So you have to perform some tests to locate and identify the culprit/s.

Tony

[pmax]

Originally Posted by Hetheca

Recently purchased a '74 targa with a 3.0 engine. I'm in OC, CA
..
Key in on position, Fuel Pump runs. It's not supposed to I know so maybe the wiring when the 3.0 was installed?

Not supposed to if the wiring is standard 3.0 but you have a transplant.

4. Still no start. It tried and backfired.
5. Realize I'm not hearing the Fuel Pump but instead a motorized Antenna that's not connected to the antenna. Passenger side front fender
6. Also realize I was hearing 2 "pump like" noises before the car stopped working.
...
- Could still be the FP Relay
- Could be the FP
- Don't think it's the CDI

Agreed. Sounds like it's starving of fuel.
3.0 has an "airflow" switch at the back of the engine which cuts off the FP. Disconnect it to eliminate the possibility. Not sure what you have, pics will help.

You guys run 89 or 91 gas?

Thanks for all of your impute, greatly appreciated.

Premium ! Always !

Have fun with the troubleshooting.

[Hetheca]

My mistake on today’s rundown.
I did get it to start before anything on my list was done today...very rough start but ran, as if the timing is off. While it was running I checked the air flap in the air filter. It was solid tight.

I will test CDI with an inductive light. As well as test csi fuel pressure.

Ordered a FP relay to rule that out. Will be here tomorrow.

Did find this late tonight. Anyone have a part number?

[bigtoad]

Just be aware as you're running through your system checks that a healthy-sounding CDI could still be faulty. I went through this on a 3.0. The CDI had the beautiful whine of a healthy unit, but the car was exhibiting random backfiring, occasional no start, didn't matter if it was hot or cold. We swapped out the CDI for a known good one, and boom the car ran great again. Also all resistance tests on the bad CDI showed no issue.

[timmy2]

No Porsche part number for that connector to your WUR.
i have them on hand for building wiring harnesses and do sell them as a kit with a new rubber boot and terminals to crimp on the wires.
PM me for my PayPal info if you want one. $12 for the kit snail mail, $17 for priority mail.

[Mixed76]

My 3.0 is from a 78, stock single plug, and I run regular gas. Compression is low, cams are mild, no need for premium.

After you get it running consistently- assuming it is unrelated, which I think it is- consider rechecking your plugs to figure out why they are fouling. Maybe too much light throttle use, maybe leaking valve stem seals.

[997at]

As Tony has suggested, it's always a good idea to check fuel pressures first (cold and warm). My advice is start here...do one thing at a time. An engine needs three basic elements working together: fuel, air, spark. Start with fuel.
I'd be happy to talk you through the fuel pressure check as would others.