1986 951 no start

[CarBot]

These CarBot answers are coming mostly from our no-start knowledge base, so it is giving pretty sound advice. Given your recent findings on the bad vacuum hose, and it subsequently starting but running poorly, I'd focus on ensuring the proper AFR, most likely vacuum related. When it runs, how much vacuum are you seeing at the FPR vacuum line, and what's the RPM. CC'ing to keep it up to speed and see what it things now.

If it now starts after fixing a bad vacuum hose but runs poorly, I’d treat that as “you found one leak, there may be more,” and agree AFR/vacuum is the most likely direction.

At the FPR vacuum line specifically, you should see steady manifold vacuum at idle. If vacuum there is low, unstable, or near zero at idle, either the engine isn’t actually getting normal manifold vacuum (big leak, late cam timing, misfire) or the FPR line isn’t truly connected to manifold vacuum (wrong port, cracked hose, check valve issue, tee feeding something it shouldn’t). RPM matters because a high idle from a leak can still show some vacuum, but it’ll often be lower than expected and “fluttery.”

Practical next checks that usually pay off on a 951 after a hose failure are confirming the FPR and damper lines are routed correctly and not swapped, smoke testing the intake/charge system (including intercooler end tanks and all the small vacuum lines), and verifying the brake booster line and check valve. Also make sure the J-boot and all clamps between AFM and turbo inlet are tight, because unmetered air there can make it run terribly.

If you can post the idle RPM, the vacuum reading at the FPR line at idle, and whether it smooths out when you pinch off the ICV hose or brake booster hose, that will usually point right at the leak area.

[zooklm1]

These CarBot answers are coming mostly from our no-start knowledge base, so it is giving pretty sound advice. Given your recent findings on the bad vacuum hose, and it subsequently starting but running poorly, I'd focus on ensuring the proper AFR, most likely vacuum related. When it runs, how much vacuum are you seeing at the FPR vacuum line, and what's the RPM. CC'ing @CarBot to keep it up to speed and see what it things now.

@CarBot Have not put a vacuum gauge on it yet. However in taking off the intercooler hard pipes to work on the vacuum lines, I found gasoline in the hard at the throttle body. I am thinking I need to take the intake manifold off in case there is other pooled fuel.

[CarBot]

Have not put a vacuum gauge on it yet. However in taking off the intercooler hard pipes to work on the vacuum lines, I found gasoline in the hard at the throttle body. I am thinking I need to take the intake manifold off in case there is other pooled fuel.

Finding gasoline in the charge pipe near the throttle body usually points to one of three things: the engine has been heavily flooded during the no-start attempts, an injector is leaking/stuck open, or the fuel pressure regulator/damper is leaking fuel into its vacuum line and letting it get pulled into the intake. It’s not normal, but it also doesn’t automatically mean you need to pull the intake manifold.

Before pulling the manifold, I’d do two quick, high-value checks. First, pull the vacuum line off the fuel pressure regulator and the fuel damper and look for any wet fuel in either vacuum port/line. If there’s fuel there, that component is bad and can absolutely cause rich running, hard starting, and fuel in the intake tract.

Second, verify whether the injectors are leaking. With the key off, the rail should hold pressure for a while; if it bleeds down quickly and you’re getting fuel smell/wetness, you may have a leaking injector or check valve issue. If you can, pull the plugs and see if one or more are wet and fuel-fouled, which can help identify a single-cylinder injector leak.

If you suspect it’s flooded, you can clear it by disabling fuel (unplug injectors or pull the DME relay) and cranking with the throttle open to blow it out, then reinstall and try again. Change the oil if you think a lot of fuel washed past the rings, because fuel dilution is hard on bearings.

Pulling the intake manifold is usually a last step unless you already have evidence of a major internal leak or you need access for injector service. If you do end up removing it, replace the gaskets and inspect all the vacuum ports and hoses carefully while it’s off.

If you tell me whether there’s fuel present in the FPR or damper vacuum line, and whether the plugs are wet on one cylinder or all of them, that will point to the most likely source.

[zooklm1]

Have not put a vacuum gauge on it yet. However in taking off the intercooler hard pipes to work on the vacuum lines, I found gasoline in the hard at the throttle body. I am thinking I need to take the intake manifold off in case there is other pooled fuel.

Finding gasoline in the charge pipe near the throttle body usually points to one of three things: the engine has been heavily flooded during the no-start attempts, an injector is leaking/stuck open, or the fuel pressure regulator/damper is leaking fuel into its vacuum line and letting it get pulled into the intake. It’s not normal, but it also doesn’t automatically mean you need to pull the intake manifold.

Before pulling the manifold, I’d do two quick, high-value checks. First, pull the vacuum line off the fuel pressure regulator and the fuel damper and look for any wet fuel in either vacuum port/line. If there’s fuel there, that component is bad and can absolutely cause rich running, hard starting, and fuel in the intake tract.

Second, verify whether the injectors are leaking. With the key off, the rail should hold pressure for a while; if it bleeds down quickly and you’re getting fuel smell/wetness, you may have a leaking injector or check valve issue. If you can, pull the plugs and see if one or more are wet and fuel-fouled, which can help identify a single-cylinder injector leak.

If you suspect it’s flooded, you can clear it by disabling fuel (unplug injectors or pull the DME relay) and cranking with the throttle open to blow it out, then reinstall and try again. Change the oil if you think a lot of fuel washed past the rings, because fuel dilution is hard on bearings.

Pulling the intake manifold is usually a last step unless you already have evidence of a major internal leak or you need access for injector service. If you do end up removing it, replace the gaskets and inspect all the vacuum ports and hoses carefully while it’s off.

If you tell me whether there’s fuel present in the FPR or damper vacuum line, and whether the plugs are wet on one cylinder or all of them, that will point to the most likely source.

The vacuum lines at the FPR and dampener are dry. I also had number 2 injector leaking that I fixed a couple days back that I didn’t tell you about.

[CarBot]

The vacuum lines at the FPR and dampener are dry. I also had number 2 injector leaking that I fixed a couple days back that I didn’t tell you about.

If the FPR and damper vacuum lines are dry, that makes those two much less likely as the source of raw fuel in the pipe. With a recently leaking number 2 injector in the mix, the simplest explanation is that the engine got flooded during the no-start period and you’re seeing leftover fuel that got pushed back through the intake during cranking and misfiring, plus whatever pooled in the intercooler/charge plumbing.

I wouldn’t pull the intake manifold just for “pooled fuel” unless you have a strong reason. I’d instead clean and dry what you can reach in the charge pipes and throttle body area, then focus on confirming the injector leak is truly gone and that the engine isn’t still running overly rich.

A practical next step is to pull all four plugs and see if any are wet or fuel-fouled, especially cylinder 2. If #2 is still noticeably different, that injector may still be dribbling or the seal/seat isn’t right. If all plugs are black/wet, think global rich condition or repeated flooding.

If you can, do a fuel pressure leakdown check. After key-on/prime, pressure should hold reasonably; if it drops quickly and you don’t have an external leak, that points back toward an injector leaking internally (or less commonly the pump check valve), and a single leaky injector can make it start and run poorly.

Since it’s now running poorly and you’ve been into vacuum lines, I’d still put a vacuum gauge on it at a true manifold source and see if idle vacuum is steady. Low and unstable vacuum usually means you still have a leak, a big hose routing issue, or a misfire.

If you share how it runs now (idle RPM, does it hunt, any smoke, fuel smell, and whether cylinder 2 plug looks wet compared to the others), I can help narrow whether you’re chasing remaining vacuum leaks or a fueling issue.

[zooklm1]

The vacuum lines at the FPR and dampener are dry. I also had number 2 injector leaking that I fixed a couple days back that I didn’t tell you about.

If the FPR and damper vacuum lines are dry, that makes those two much less likely as the source of raw fuel in the pipe. With a recently leaking number 2 injector in the mix, the simplest explanation is that the engine got flooded during the no-start period and you’re seeing leftover fuel that got pushed back through the intake during cranking and misfiring, plus whatever pooled in the intercooler/charge plumbing.

I wouldn’t pull the intake manifold just for “pooled fuel” unless you have a strong reason. I’d instead clean and dry what you can reach in the charge pipes and throttle body area, then focus on confirming the injector leak is truly gone and that the engine isn’t still running overly rich.

A practical next step is to pull all four plugs and see if any are wet or fuel-fouled, especially cylinder 2. If #2 is still noticeably different, that injector may still be dribbling or the seal/seat isn’t right. If all plugs are black/wet, think global rich condition or repeated flooding.

If you can, do a fuel pressure leakdown check. After key-on/prime, pressure should hold reasonably; if it drops quickly and you don’t have an external leak, that points back toward an injector leaking internally (or less commonly the pump check valve), and a single leaky injector can make it start and run poorly.

Since it’s now running poorly and you’ve been into vacuum lines, I’d still put a vacuum gauge on it at a true manifold source and see if idle vacuum is steady. Low and unstable vacuum usually means you still have a leak, a big hose routing issue, or a misfire.

If you share how it runs now (idle RPM, does it hunt, any smoke, fuel smell, and whether cylinder 2 plug looks wet compared to the others), I can help narrow whether you’re chasing remaining vacuum leaks or a fueling issue.

I did get it to run briefly though pumping the accelerator and it ran poorly with lots of smoke and fuel rich smell. It does not idle, though.

[CarBot]

I did get it to run briefly though pumping the accelerator and it ran poorly with lots of smoke and fuel rich smell. It does not idle, though.

That sounds like it’s still massively rich and/or still flooded, and the “won’t idle” part often goes with either a big vacuum leak or the idle control system not being able to manage airflow. Since you also had a known leaking injector recently, I’d keep fuel delivery at the top of the list.

First thing I’d do is stop trying to start it repeatedly and check the oil for fuel dilution. If the dipstick level is high or it smells like gasoline, change the oil before more run time.

Next, pull the plugs again and read them. If they’re wet with fuel, dry/replace them and clear the cylinders. A quick way is to disable fuel (unplug the injector connectors or pull the DME relay) and crank with the throttle held open for a bit to blow it out, then re-enable fuel and try a normal start. If it only runs when you pump the pedal, that can be consistent with a bad base mixture or a big air leak, but the heavy smoke and raw fuel smell points more to overfueling.

Then verify the injector situation is truly fixed. Even a slight dribble from one injector can make it start, smoke, stink, and refuse to idle. If you can do a leakdown test on the rail and/or pull the rail with injectors still attached (carefully, with rags and safety in mind) you can sometimes spot a dribbler. If cylinder 2 plug is consistently wetter than the others, that’s a big clue the injector is still not sealing.

After that, I’d check for a major vacuum/charge leak you may have introduced while working on lines and intercooler pipes. On a 951, a big leak in the intake/charge plumbing can make it run terribly and not idle, and it can also make you chase mixture problems that aren’t really “fuel” problems. Make sure the J-boot, all clamps, intercooler connections, and any large manifold hoses (brake booster line, ICV hoses) are properly seated and not split.

One more common contributor to pig-rich running is the DME coolant temp signal (the blue sensor). If it’s unplugged or the connector is bad, the DME can default rich. It usually still starts, but it can run awful and smoke. Make sure that connector is clean and tight.

If you can answer two quick things, it’ll narrow it a lot. Are the plugs wet after a failed start attempt, and is one cylinder (especially #2) noticeably worse than the others. Also, is the smoke black (sooty) like fuel-rich, or more white/gray.

[zooklm1]

I did get it to run briefly though pumping the accelerator and it ran poorly with lots of smoke and fuel rich smell. It does not idle, though.

That sounds like it’s still massively rich and/or still flooded, and the “won’t idle” part often goes with either a big vacuum leak or the idle control system not being able to manage airflow. Since you also had a known leaking injector recently, I’d keep fuel delivery at the top of the list.

First thing I’d do is stop trying to start it repeatedly and check the oil for fuel dilution. If the dipstick level is high or it smells like gasoline, change the oil before more run time.

Next, pull the plugs again and read them. If they’re wet with fuel, dry/replace them and clear the cylinders. A quick way is to disable fuel (unplug the injector connectors or pull the DME relay) and crank with the throttle held open for a bit to blow it out, then re-enable fuel and try a normal start. If it only runs when you pump the pedal, that can be consistent with a bad base mixture or a big air leak, but the heavy smoke and raw fuel smell points more to overfueling.

Then verify the injector situation is truly fixed. Even a slight dribble from one injector can make it start, smoke, stink, and refuse to idle. If you can do a leakdown test on the rail and/or pull the rail with injectors still attached (carefully, with rags and safety in mind) you can sometimes spot a dribbler. If cylinder 2 plug is consistently wetter than the others, that’s a big clue the injector is still not sealing.

After that, I’d check for a major vacuum/charge leak you may have introduced while working on lines and intercooler pipes. On a 951, a big leak in the intake/charge plumbing can make it run terribly and not idle, and it can also make you chase mixture problems that aren’t really “fuel” problems. Make sure the J-boot, all clamps, intercooler connections, and any large manifold hoses (brake booster line, ICV hoses) are properly seated and not split.

One more common contributor to pig-rich running is the DME coolant temp signal (the blue sensor). If it’s unplugged or the connector is bad, the DME can default rich. It usually still starts, but it can run awful and smoke. Make sure that connector is clean and tight.

If you can answer two quick things, it’ll narrow it a lot. Are the plugs wet after a failed start attempt, and is one cylinder (especially #2) noticeably worse than the others. Also, is the smoke black (sooty) like fuel-rich, or more white/gray.

Plugs were not wet and they all looked similar. Smoke color was hard to determine but did have a fuel smell component

[CarBot]

Plugs were not wet and they all looked similar. Smoke color was hard to determine but did have a fuel smell component

If the plugs aren’t wet and all look similar, that makes a single stuck-open injector less likely right now. The fuel smell and smoke still suggest it’s running rich when it does catch, but the “only runs with pumping and won’t idle” also fits a big unmetered air leak or idle air control problem, especially after you’ve had the intercooler pipes and vacuum lines apart.

I’d put a vacuum gauge on a true manifold source as your next step. If you have very low or unstable vacuum at idle attempt, that points strongly to a leak or a major mechanical/timing issue. If vacuum is decent but it still won’t idle, focus on the idle control valve and its hoses, and the throttle body/idle switch adjustment. On these cars, if the DME doesn’t see “idle” from the throttle switch, idle control can be poor and you end up having to hold the throttle to keep it running.

Since you found fuel in the pipe earlier, I’d also pull the intercooler and drain/clean it if you haven’t. A surprising amount of fuel can sit in the intercooler/charge plumbing after flooding and make the first few run attempts smoky and nasty even after the root cause is fixed.

Two other quick checks that often matter after a no-start and lots of cranking are fuel pressure and the blue DME temp sensor connection. Low fuel pressure can cause it to only run with throttle input, and a bad/loose blue temp sensor connector can skew mixture badly. If you can measure fuel pressure at the rail, that’s a very strong data point.

If you tell me whether the idle switch clicks and shows continuity at closed throttle, and whether you’ve smoke-tested the intake/charge system (or at least rechecked every coupler and the ICV/brake booster hoses), I can help you pick the most likely culprit.

[Tom]

@CarBot the injectors fire straight above the head on the 944, after air has been pulled through the filter, turbo, intercooler and its pipes, and intake manifold -- the injectors sit at the very end of that path, so very unlikely that fuel flowed upstream against the flow of vacuum to pool in the intercooler pipes. A leaking fuel pressure regulator is common, however, and could spread fuel around the intake path. I would be inclined to quadruple check for signs of gas in any of the vacuum lines, including the one to the bypass valve.