First start after 25 years - problems Options

[spencercanon]

Hi all this is my first post here! I recently picked up a ’75 1.8 that was last registered in 2001! Pretty good barn find, in my opinion. It was up in the high desert of California, so no rust, great mechanicals, all the electrics work. Just flaking paint, decayed interior …and an engine that probably hasn’t run since the Clinton Administration.

The TLDR is the car has started and run for 10 seconds but now won’t start at all.

A quick timeline of what I’ve done/tested:
- Dropped the engine, adjusted valves (encountered something strange that I’ll ask about later)
- Old starter could barely turn the engine over. Replaced it with a hi-torque.
- good compression
- Replaced the old broken bellows thermostat
- New fuel lines, vac lines, spark plugs and wires
- deleted EGR system
- Fuel pump was getting power but dead - replaced it.
- Coil’s good. Cap and rotor look good. Points gapped.
- The L-Jet AFM had been opened and the adjustment wheel inside was so loose that it the flap wasn’t closing fully so the pump was running continuously. I rotated the wheel until there was enough tension to turn off the fuel pump. (I would have normally never touched the AFM!)

Put the engine back in and the car started on the key immediately, ran for 10 seconds and died. I tried again, it started and ran for 5 seconds, then popped loudly back up the intake with enough force to blow the intake boot off the AFM. Since then, it hasn’t started.

Couple notes:
- after the pop, I felt like the intake pipe connector hoses were probably leaking, so I put hose clamps on them. With those clamped down and fresh vac lines everywhere, I’m pretty sure there aren’t any more leaks.
- oil filler breather nipple broke so I’ve taped it off until I can get a new one. But I’m not sure how this affects the vacuum… should it be left open for now?
- I don’t know the fuel pressure but it does have a new pump and lines so I’d be surprised if pressure is the problem.
- tested injector ballasts and got correct ohm readings
- It did start and run on its own spark and fuel, so I assume ECU and injectors are OK.
- the AFM is obviously an issue … probably considerably off. But again, the car did at least start a few times.

So now what?
- I’d like to check/test anything I can before I start buying replacement components.
- Are there baseline settings for idle speed screw, and at least a “best guess” AFM setup?
- Should I just buy another AFM now, knowing this one may never be right again?
- could the intake backfire have damaged something?

Thanks in advance for your thoughts!

[technicalninja]

"Will it start", "Does it turn over"

I never understood that logic.


Take an engine that has sat for 5/10/15/20/25/+ years and the first thing people do is try to "turn it over".

If there was even a hint of moisture or corrosion in that engine (likely) you just ruined all the bearings and possibly scratched the rings, pistons and cylinders.

(IMG:style_emoticons/default/confused24.gif)

That sounds good to me. But. What do you do given the situation? I feel like a hand on a wrench turning the crank might point out problems. Porsche never seems all that enthusiastic about getting a wrench on the crank though, so it isn’t easy.

This is what I'd do on an engine that I knew nothing about. If I found trouble it would get addressed before the next step.

Borescope FIRST!
Add 30ccs Marvel Mystery oil to each cylinder.
Remove valve covers.
Remove rocker arms.
Verify no broken springs/valves stuck open.

Rotate engine by hand. You CAN rotate the engine by placing in gear and rolling car OR locking one rear wheel and rotating the other.
The only problem with this is you lose the "feel" of minor trouble that you can detest via a breaker bar.
I have modified an old cheap torque wrench (beam style) that I use the crap out of for just this purpose.
During rotation of a 4 cylinder, you should be able to "feel" two spots that require reduced torque. These are when the pistons reach both TDC and BDC.
So, some minor drag with two soft spots is what I'd be hunting.

And, if you have no compression (plugs out) and no valvetrain loading (rocker arms off) the amount of torque required to spin the engine over should be very small.

Really, you should be able to easily do this using the fan alone. Lots of folks use the alternator pully nut.

Rotate engine by hand through at least 720 degrees of rotation and check for roughness/binding.

Do leak down tests. LD testing is a BUNCH easier without the valves involved.
"Bonk" each valve lightly (under LD pressure) with a brass hammer to verify movement and not sticking open. You should notice your LD numbers improving with number of bonks; this is blowing debris from the valve seating interface.

If I made it to this point, I'd start prepping for an actual restart.

Change oil/filter. Clean strainer.
Disable fuel system and ignition system.
Install mechanical oil pressure gauge (shop tool).

Put shop towels over spark plug holes. Might get messy.

Spin engine with starter.
Spin engine until NO MORE marvel mystery oil is ejected from cylinders.

Reinstall/adjust rocker arms, valve covers. Change tube O-rings is not a bad thing to add

Run compression tests

Add ignition

Start on B12.

Add fuel.

You WILL have poor leak down numbers and compression readings before you run the engine both up to temperature and under load. Just revving the engine up is NOT enough. Up hills at 75% throttle or better is "load" in my book.

30-50% leak downs wouldn't bother me pre-run. 60psi comp test wouldn't either.

Red flags are numbers vastly different from each other.

Go drive "sportingly" and retest comp/LD hot.


Anyone think of something I missed?