914 Owner’s Guide
How to Revive Your Porsche 914: Bringing It Back From the Dead
This article originally appeared as a feature in PMB Performance’s October newsletter, so we couldn’t resist giving this 914 revival guide a little Halloween spirit. The advice, however, applies any time of year, especially when the car in your garage has been playing dead for a while.
In our first Porsche 914 guide, we told you to buy the body first. In the second, we covered what to do once you had a running 914 in your garage. But what happens when you find the right car, drag it home, turn the key… and nothing happens?
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Maybe it clicks. Maybe it cranks enthusiastically without firing. Maybe it coughs to life for three seconds and immediately returns to the grave. Before you order a starter, blame the fuel injection, convert it to carburetors, or start searching for a replacement engine, there is a much better approach. A non-running 914 is not necessarily a dead 914. You simply need to work through it one system at a time. |
Playing dead, not dead. Work through it one system at a time. |
First, Figure Out What You Actually Bought
Before touching anything, identify exactly what is in the car. Stock four-cylinder 914s generally used D-Jetronic fuel injection on the 1.7- and 2.0-liter engines and L-Jetronic on the 1.8. After five decades, however, many cars have been converted to carburetors, received different engines, or accumulated a mixture of parts from several model years.
Take pictures of the engine compartment, distributor, fuel injection components, wiring and hose routing before taking anything apart. Do not assume the engine lid badge tells the entire story.
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Turn it by hand first. If it will not rotate freely, the starter is the wrong tool for finding out why. |
If the car has been sitting for years, resist the temptation to throw in a battery and see what happens. Remove the spark plugs and make sure the engine can rotate freely by hand. Inspect the plugs, look into the cylinders if you have access to a borescope, and make sure there is no obvious evidence of water, corrosion, or mechanical binding. While you are there, look underneath the engine tin and around the cooling fan. Mice, shop rags, leaves, and other debris have an uncanny ability to find their way into an air-cooled engine. A 914 can run surprisingly well while something is blocking its cooling air, right up until it doesn’t. |
PMB Pro Tip: If the engine will not turn freely by hand, stop. The starter motor is not the proper tool for determining why an engine is stuck.
Give It Fresh Blood
Gasoline that has been sitting for years does not become good gasoline because you pour five gallons of fresh fuel on top of it. Drain the old fuel and inspect the tank for rust, sediment, and contamination. The 914 also has a pickup screen inside the fuel tank that can become restricted, so do not overlook it simply because you plan to install a new external fuel filter.
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Next, follow the fuel system from the tank all the way to the engine. Inspect the rubber hoses under the tank, the lines running through the center tunnel, the connections at the engine compartment, and the short hoses associated with the injectors or carburetors. If the age or condition of a rubber fuel hose is questionable, replace it with the correct fuel-compatible hose for the system. Pay particular attention to the fuel lines that disappear from sight. The easiest hose to inspect is not necessarily the one most likely to ruin your day. |
Follow the fuel from the tank to the engine, including the hoses you cannot easily see. |
Change the engine oil and filter before subjecting a long-dormant engine to repeated starting attempts. Pay attention to what comes out. Fuel contamination, water, metallic debris, or anything else unusual deserves investigation before you continue.
One important Type 4 warning: the oil-strainer fastener is tightened to a very low torque compared with a conventional drain plug. Do not lean on it with a large wrench. Over-tightening that fastener can create a much larger problem than the oil change you were attempting to perform.
If It Does Not Crank
A no-crank condition is fundamentally different from an engine that cranks but will not start. Start with the basics before buying a starter.
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Easy to forget, and the starter depends on it. The ground strap above the transmission. |
Charge and test the battery, clean and inspect both battery connections, and then examine the major ground paths. One particularly important 914 ground is the transmission-to-body ground strap. It lives above the transmission and is easy to forget, yet the starter depends on it to complete the electrical circuit. Next, determine whether the starter solenoid is actually receiving its start signal when the key is turned. If it is not, work backward through the ignition-switch circuit and wiring rather than immediately replacing the starter. |
Some 914s were also equipped with a seat-belt starter interlock system. If your car retains that equipment, the wiring and control unit beneath the passenger seat can become part of the diagnosis.
PMB Pro Tip: Before replacing a starter, make sure it actually has battery power, a good ground, and a proper start signal.
If It Cranks but Will Not Start
Once the engine is turning normally, you need three basic ingredients: compression, ignition, and fuel.
Start with ignition because it is relatively easy to prove. Use an appropriate spark tester and verify that you have a strong, consistent spark. Check the coil connections, distributor, cap, rotor, plug wires, and ignition points or electronic ignition components where fitted.
The four-cylinder firing order is 1-4-3-2, but do not simply copy the plug-wire position from someone else’s engine. Establish cylinder No. 1 at top dead center on the compression stroke and verify where the rotor is actually pointing. After decades of repairs and distributor changes, appearances can be deceiving.
Do not assume that a newly installed ignition part is automatically correct. Incorrect electronic ignition modules, poor connections, damaged distributor components, and improperly installed rotors can create a new no-start problem while you are trying to fix the old one.
Once ignition is established, move to fuel delivery.
Hearing the Fuel Pump Is Not Enough
A fuel pump making noise tells you only that the electric motor inside the pump is doing something. It does not tell you that the engine has the proper fuel pressure.
Put a gauge on the system.
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D-Jetronic cars generally operate at roughly 29 PSI. L-Jetronic cars operate at a somewhat higher pressure, roughly in the mid-30 PSI range under the appropriate test conditions. Carbureted cars operate at dramatically lower pressure, which is why an injection pump and a carburetor require very different fuel-pressure strategies. Correct pressure also does not prove that the injectors are actually opening. If you have pressure but dry spark plugs, the next question becomes whether the injectors are receiving a signal and delivering fuel. |
A running pump is not the same as correct pressure. Put a gauge on it. |
This is where the diagnosis needs to split between D-Jet and L-Jet.
D-Jet: Check the Simple Things Before Blaming the ECU
On a stock D-Jet car, you should normally hear the fuel pump run briefly when the ignition is switched on. If you do not, investigate the relay board, fuel-pump relay, fuse contacts, and associated wiring.
There is also an easily overlooked failure point in the auxiliary air regulator circuit. Its electrical heater shares part of the fuel-pump power circuit. Damaged wiring at the regulator can blow the fuse and leave you chasing what appears to be a fuel-pump problem.
Next, check the fuel-injection grounds on the engine. D-Jet uses dedicated ground connections attached to the engine case. Dirty, loose, or disconnected grounds can cause seemingly mysterious injection problems even when the battery ground is perfectly fine.
Another particularly important D-Jet detail is inside the distributor. In addition to the ignition points, D-Jet uses a separate set of trigger contacts to tell the injection system when to fire the injectors. That means you can have perfectly good ignition spark and still have no injector pulse.
The cylinder-head temperature sensor is another critical component. A disconnected or failed sensor circuit can cause an extremely rich condition and flood the engine. Inspect the sensor wiring carefully before assuming the sensor itself has failed.
Finally, inspect the manifold-pressure sensor and its vacuum hose. The hose needs to be intact and the sensor needs to hold vacuum properly. Resist the temptation to adjust the sensor internally simply because the engine will not run correctly. Adjustment should come only after the rest of the system has been proven healthy.
PMB Pro Tip: On D-Jet, prove power, grounds, trigger signals, and sensor inputs before blaming the ECU.
L-Jet: Different System, Different Rules
The 1.8-liter L-Jet system behaves differently enough that D-Jet troubleshooting advice can actually send you in the wrong direction.
For example, a stock L-Jet car does not normally give you the same brief fuel-pump run when you first turn the key. The pump is controlled through the double relay, cranking circuit, and airflow meter. So the absence of a two-second fuel-pump sound does not automatically mean something is wrong.
If an L-Jet engine fires while cranking but immediately dies when the key returns to the run position, investigate whether the fuel pump continues to operate after cranking. The double relay, airflow-meter contacts, and associated wiring become prime suspects.
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Check the underside of the intake boot. L-Jet does not forgive unmetered air. |
L-Jet is also extremely sensitive to air leaks. Inspect the large intake boot between the airflow meter and throttle body carefully, especially its underside. Check the intake-runner hoses, injector seals, and vacuum hoses. Even the oil-filler cap seals and filler housing can introduce unmetered air into the system. If the engine has backfired through the intake, make sure the airflow-meter flap still moves freely and has not been damaged. |
Do not forget the injector electrical connections either. A bad connector or poor contact at a single injector can create a dead cylinder that looks much more complicated than it actually is.
PMB Pro Tip: On L-Jet, never underestimate an air leak. Air entering the engine without passing through the airflow meter can create all sorts of strange behavior.
What If Someone Converted It to Carburetors?
A carburetor conversion changes the fuel system, but it does not eliminate the need for proper diagnosis.
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If the car has been sitting, expect dried fuel deposits and varnish inside the carburetor bowls, jets, and passages. Check float operation, needle valves, and linkage movement before attempting to tune anything. Most importantly, verify fuel pressure. Carburetors require much lower fuel pressure than the original electronic injection systems. Excessive pressure can overwhelm the float valves and flood the engine. Once the carburetors are mechanically clean and the ignition system is correct, establish the manufacturer’s baseline settings and synchronize the carburetors properly. Randomly turning mixture screws until the engine stays running generally creates more problems than it solves. |
Clean them, check the pressure, then tune. Never the other way around. |
It’s Alive! Now Don’t Get Carried Away
Once the engine is ready for its first controlled start, establish oil pressure before allowing it to run. Disable fuel or ignition as appropriate and crank the engine in short intervals while watching for oil-pressure indication.
When you are ready for the actual start, do it outside in a well-ventilated area with the car securely in neutral and an appropriate fire extinguisher nearby. Having a second person watch the engine compartment for fuel or oil leaks is extremely helpful.
When the engine starts, watch the oil pressure, listen carefully, and look for leaks. Do not immediately start revving it because you are excited to hear it run. Fuel pouring onto the engine, no oil-pressure indication, or a serious mechanical noise means shut it down and find the problem.
And remember, a running 914 is not necessarily a roadworthy 914.
Before that first drive, inspect the brakes, tires, steering, suspension, wheel bearings, throttle operation, and clutch. Make sure the car stops before worrying about how quickly it goes.
Bringing the Dead Back to Life
Reviving an old Porsche 914 is not about seeing how many parts you can replace before something finally happens. The real objective is to diagnose the car methodically, repair the cause of each problem, and verify the result before moving on.
Sometimes the answer will be substantial mechanical work. Other times it may be a corroded ground, cracked intake boot, plugged fuel pickup, or electrical connector that has quietly been waiting thirty years for someone to find it.
Back from the dead, and built to stay that way.
Either way, take your time and work through the systems one by one. The goal is not simply to bring your 914 back from the dead for Halloween.
The goal is to make sure it stays alive.