Starting issue - or normal?

patssle · 06:32 AM

My 911 is in storage for now until I can figure out what the heck everything is (wires are everywhere). Occasionally I start it just to get it running. I previously drove it from Austin to Houston and did not have any problems with the engine.

When it starts, I have the keep the gas pedal pushed all the way and it will making deep popping sounds in the air box and barely keep turning over for 10-20 seconds, then all of a sudden it will highly rev and I'll be able to remove my foot from the pedal and it will idle fine. The last time I started it, the car shook a little too during this process, and it took longer - like the problem is getting worse.

Is this a normal fuel injection thing or do I have a problem?

Walter_Middie · Walter_Middie's Garage

This is not normal - or even close. With my 75, starting from cold, I lift the hand throttle and turn the key. It starts immediately, and I adjust the idle to about 1500 RPM with the hand throttle. Then put it in reverse, and I'm off. No issues, no drama.

You will most likely need to check your fuel system pressures. You can purchase these test kits fairly cheaply. Your system may only need adjustment - or you may have vacuum issues. I'd start by making sure your tune-up is good, then check fuel system pressures. If all that is OK, then I'd be looking for vacuum leaks.

patssle · 08:01 AM

Ok, I didn't think it was normal, but I have no experience with older fuel injection systems.

I'm actually going to put carbs on this engine, so I don't want to buy anything to fix the problem - if it is just the fuel injection or fuel system (since I'll have to convert to 3.5 psi anyways). But I'll check what I can with what I have,.

ossiblue · 08:15 AM

After reading your post, your problem may not be that abnormal. My understanding is the engine is sitting for long periods of time without being started. This would allow the fuel system to lose residual pressure. The symptoms you describe sound like fuel starvation from the fact that the system has to re-pressurize before the car starts. This could be due to a faulty fuel accumulator or bad check valve in the fuel pump. Next time, try this: remove the air filter and turn on the key to activate the fuel pump. Gently lift the plunger that's inside the air intake until you hear the injectors "squeal"--this pressurizes the system and primes the injectors (do not hold the plunger up for more than 5-8 seconds as you don't want to flood the cylinders.) Now, lift the hand throttle like Rex posted (don't push on the gas pedal) and start the car. If it starts and runs, your problem was lack of residual pressure which can easily happen if the car has sat for extended periods.

BTW, if your car doesn't have a pop off valve in the air box, you're flirting with disaster trying to start the car as you've been doing. One backfire through the intake could blow that plastic box apart and then you'll never be able to get it started. Pushing fully on the gas while trying to start is too risky. Use the starting procedure outline by Rex, even if you do have a pop off valve installed.

patssle · 10-04-2010, 09:52 AM

When I say sitting, I've been starting it once a week or every other week. So I've only done it a couple times now (bought it in late August). Yeah I've read about the air box exploding on these cars.

As I said, I drove it home with no problem. When it was in Austin it started beautifully.

I will try your method when I get home this evening. I didn't know it has a hand throttle though, especially since it's not the stock engine. What does it look like, I haven't seen it?

Thanks!

hessel1974 · hessel1974's Garage

The handthrottle is the lever left of the handbrake lever (small black round knob) manually moves the throttle rod so that the engine get's more gas idling when cold. Also makes a very basic '70s cruise control

kach22i · kach22i's Garage

This is a CIS engine, right?

And the weather has recently been getting colder, right?

You may need to richen your mixture a little.

patssle · 10-04-2010, 10:49 AM

Don't recall a knob there, but maybe I've missed it. Will look.

Yes CIS. If by cold, you mean its low 80s instead of 90s...then yes it's "colder"

Walter_Middie · Walter_Middie's Garage

patssle,

Quote:

I didn't know it has a hand throttle though, especially since it's not the stock engine. What does it look like, I haven't seen it?

I see from your signature that you have a 1981 3.0L engine. Depending on how the CIS was connected, you may or may not have a hand throttle.

Who did the engine conversion?

patssle · 11:03 AM

Quote:

Originally Posted by Walter_Middie

I see from your signature that you have a 1981 3.0L engine. Depending on how the CIS was connected, you may or may not have a hand throttle.

Who did the engine conversion?

It was done by the PO - but don't know if he or a shop did it. And can't find out.

Is it possible to "hand throttle" from the engine bay with a 2nd person in case I don't have it connected? What's the difference between the mechanical linkage between the gas pedal and a hand throttle...don't they do the same thing?

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Walter_Middie

This is not normal - or even close. With my 75, starting from cold, I lift the hand throttle and turn the key. It starts immediately, and I adjust the idle to about 1500 RPM with the hand throttle. Then put it in reverse, and I'm off. No issues, no drama.

You will most likely need to check your fuel system pressures. You can purchase these test kits fairly cheaply. Your system may only need adjustment - or you may have vacuum issues. I'd start by making sure your tune-up is good, then check fuel system pressures. If all that is OK, then I'd be looking for vacuum leaks.

Rex,

I don't believe the '81 SC engines utilize a hand throttle like those in the '73.5-'74-'75 CIS engines. The car is a '74 chassis with '81 updated engine.

Tony

Por_sha911 · Por_sha911's Garage

BTW, starting the car without getting it up to operating temp is not a good idea.

James Brown · James Brown's Garage

Crap, don't worry about the CIS stuff, rip it out and transition to PMO carbs asap. However, a and throttle is advised as there is no choke on any Porsche carb. I can do the whole conversion for $6k out the door and that's with SSI exhaust!!

psalt · 10-04-2010, 11:21 AM

Normal for an 81 SC with lambda CIS, it should crank for one or two seconds, fire and run at a fast idle, 1200-1500 rpm, for several minutes, dependings on temp, then settle to a slightly rythmic 950 rpm idle. You should not touch the throttle at all during starting, there is no hand throttle, and you should be able to drive off almost immediately after starting. If not, something is out of spec or not working. My advice would be to learn about all the components, temp switches, throttle switches, etc. fitted to your specific engine, then figure out what is wrong.

patssle · 10-04-2010, 11:46 AM

Quote:

Originally Posted by James Brown

Crap, don't worry about the CIS stuff, rip it out and transition to PMO carbs asap. However, a and throttle is advised as there is no choke on any Porsche carb. I can do the whole conversion for $6k out the door and that's with SSI exhaust!!

Oh that's the plan! I got some Weber 40IDA3Cs in great condition for a major steal. Though, my 914 with dual Webers doesn't have a choke and even if it sits for a month, boy it starts right up perfectly every single time. And I haven't touched the Webers since I bought the car a year ago.

Quote:

My advice would be to learn about all the components, temp switches, throttle switches, etc. fitted to your specific engine, then figure out what is wrong.

Normally, I would agree 100% with you. But I'm tearing the CIS off and have no plans to drive the car again with CIS - and having never touched fuel injection before, I would have to do a ton of reading.

I just wanted to make sure the engine is ok, and from what people are writing - I'm good to go for the conversion. But I will try some of the things mentioned with the CIS.

James Brown · James Brown's Garage

There you go!!

patssle · 10-04-2010, 06:42 PM

Tried the plunger, didn't have any effect. Looked at all the freaking wires and electronics - and said GRRR. Way too many electronics for my taste - especially with me coming from the 914. Too much to learn for a system I won't be driving with.

Can't wait to get that fuel injection out of my car! 2 carbs and a mechanical linkage - easy to diagnose and easy to fix. No sensors, no wires, no computers, no exploding air boxes.

I'll fix my problem by installing carbs

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by patssle

Tried the plunger, didn't have any effect. Looked at all the freaking wires and electronics - and said GRRR. Way too many electronics for my taste - especially with me coming from the 914. Too much to learn for a system I won't be driving with.

Can't wait to get that fuel injection out of my car! 2 carbs and a mechanical linkage - easy to diagnose and easy to fix. No sensors, no wires, no computers, no exploding air boxes.

I'll fix my problem by installing carbs

patssle,

Save those CIS components and I'll buy them from you. Or post them at the 'for sale section'. Good luck.

Tony

patssle · 10-04-2010, 07:21 PM

Absolutely, it'll be for sale eventually.

patssle · 10-19-2010, 04:10 PM

Well, started it again today. This time didn't press on the accelerator at all, and the car started right up without any popping. But it still has a running issue. Take a look at the video and listen, what do you guys think? I'm just curious on what is causing it, I won't be driving it anymore with the CIS.