'86 951 No Start, Fuel Related?
05-24-2010, 11:51 AM
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'86 951 No Start, Fuel Related?
Repost from general 944 forum, maybe some here have ideas?
First off, thanks in advance to anyone who can help with this.
My car hasn't run in just under a year. I worked on it a lot last spring, ran it a few times last summer, and in the fall after replacing the cooling fan thermoswitch in the radiator, noticed a fuel leak over the header. It was cold outside by that point, so I let it sit for the winter (no garage). I just installed new LR lines, and the car won't start. When turning the key, it kicks a few times like it wants to start, but won't run.
If I remove the fuel pump sender fuse, the engine runs for about 3 seconds and dies, as one would expect a car with no fuel pump to do. From this, I concluded that spark is good and the problem must be fuel related. I thought the FPR may have failed shut and the engine was getting too much fuel to start and idle. I disconnected the fuel return line from the FPR and ran a new piece of line from the FPR into a container and tried to start the car. Same no-start condition and fuel gushed out, so I figured it can't be getting too much fuel.
Other troubleshooting steps I've taken:
Replaced DME relay with new one
Checked speed & reference sensors w/ multimeter a la Clarks Garage
Bypassed factory alarm a la Clarks Garage
Check plug wire routing, cap & rotor condition: good
Unplugged one fuel injector, tried to start, no appreciable difference
Listened for injectors firing when trying to start: yes, they are ticking
Unplugged AFM, tried to start, no difference
Then I noticed something bad: milkshake in oil. Coolant still looks fine. My first thought was bad headgasket allowing milkshake into the cylinders and preventing the engine from starting, but then why is it able to run (briefly) without the fuel pump? Furthermore, the car is barely modded (boost enhancer, that's it) and I didn't run it hard at all last summer. It ran fine until an electrical problem (thermoswitch) sidelined it. I have trouble believing that it blew the HG just from sitting. I can also see some oil leakage around the oil cooler, so I think it's bad seals there causing the milkshake. I know I need to solve the milkshake problem before driving the car, but I'd like to at least get it running before jumping into another project.
Any ideas? Can anyone explain why the car will run for a few seconds without the fuel pump fuse, but not at all with it? Is it definitely the headgasket and I'm just in denial? Is there a way to prove the HG is bad without taking half the engine apart?
Thanks for reading this far and thanks again to anyone who can shed some light on this.
First off, thanks in advance to anyone who can help with this.
My car hasn't run in just under a year. I worked on it a lot last spring, ran it a few times last summer, and in the fall after replacing the cooling fan thermoswitch in the radiator, noticed a fuel leak over the header. It was cold outside by that point, so I let it sit for the winter (no garage). I just installed new LR lines, and the car won't start. When turning the key, it kicks a few times like it wants to start, but won't run.
If I remove the fuel pump sender fuse, the engine runs for about 3 seconds and dies, as one would expect a car with no fuel pump to do. From this, I concluded that spark is good and the problem must be fuel related. I thought the FPR may have failed shut and the engine was getting too much fuel to start and idle. I disconnected the fuel return line from the FPR and ran a new piece of line from the FPR into a container and tried to start the car. Same no-start condition and fuel gushed out, so I figured it can't be getting too much fuel.
Other troubleshooting steps I've taken:
Replaced DME relay with new one
Checked speed & reference sensors w/ multimeter a la Clarks Garage
Bypassed factory alarm a la Clarks Garage
Check plug wire routing, cap & rotor condition: good
Unplugged one fuel injector, tried to start, no appreciable difference
Listened for injectors firing when trying to start: yes, they are ticking
Unplugged AFM, tried to start, no difference
Then I noticed something bad: milkshake in oil. Coolant still looks fine. My first thought was bad headgasket allowing milkshake into the cylinders and preventing the engine from starting, but then why is it able to run (briefly) without the fuel pump? Furthermore, the car is barely modded (boost enhancer, that's it) and I didn't run it hard at all last summer. It ran fine until an electrical problem (thermoswitch) sidelined it. I have trouble believing that it blew the HG just from sitting. I can also see some oil leakage around the oil cooler, so I think it's bad seals there causing the milkshake. I know I need to solve the milkshake problem before driving the car, but I'd like to at least get it running before jumping into another project.
Any ideas? Can anyone explain why the car will run for a few seconds without the fuel pump fuse, but not at all with it? Is it definitely the headgasket and I'm just in denial? Is there a way to prove the HG is bad without taking half the engine apart?
Thanks for reading this far and thanks again to anyone who can shed some light on this.
05-24-2010, 02:00 PM
#2
Hmmm. Well if it's a HG I would expect the same behavior regardless of the fuel pump fuse.
Let me make sure I've got this right: So if the fuse is in, you crank and crank, and no start. Hop out, pull the fuse, hop back in, hit the key, instantly it starts, runs for 3 seconds, then stalls?
No other steps or periods of time in between pulling the fuse and getting the car to start or not start? How old is the fuel in the car?
Milkshake isn't good either but may be unrelated to one another. I'd change the oil anyways before you continue messing with it, just for good measure.
Let me make sure I've got this right: So if the fuse is in, you crank and crank, and no start. Hop out, pull the fuse, hop back in, hit the key, instantly it starts, runs for 3 seconds, then stalls?
No other steps or periods of time in between pulling the fuse and getting the car to start or not start? How old is the fuel in the car?
Milkshake isn't good either but may be unrelated to one another. I'd change the oil anyways before you continue messing with it, just for good measure.
05-24-2010, 02:28 PM
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You've got it exactly right.
I was talking to a friend about it over lunch today, and he brought up the possibility of bad fuel, too. I didn't consider that because it flows fine through the rail. The fuel is at least a year old, I would say.
Is it plausible that the old fuel gunked up the injectors and caused them to get stuck open? Based on the little I know about injectors, it seems more likely that they'd get stuck shut, but I suppose anything's possible. This could cause an overly rich condition and explain why the car would run without the fuel pump. However, I can hear the injectors ticking when trying to start. Would they still tick if they were stuck?
I was talking to a friend about it over lunch today, and he brought up the possibility of bad fuel, too. I didn't consider that because it flows fine through the rail. The fuel is at least a year old, I would say.
Is it plausible that the old fuel gunked up the injectors and caused them to get stuck open? Based on the little I know about injectors, it seems more likely that they'd get stuck shut, but I suppose anything's possible. This could cause an overly rich condition and explain why the car would run without the fuel pump. However, I can hear the injectors ticking when trying to start. Would they still tick if they were stuck?
05-24-2010, 05:28 PM
#4
And it's repeatable? You can go back and forth, over and over, making the car start/not start just by pulling/installing the fuse?
(Just trying to ascertain whether or not you were just lucky the one time you pulled the fuse and the car started.)
When it DOES start and run for those 3 seconds, does it fire immediately to life and sit at idle, or does it kinda stumble stumble sputter up to idle?
What kind of shape is the battery in? Just before I replaced the battery in mine this past spring, I noticed the car was difficult to start once it got hot. (It would start, but kinda slowly creep up to idle.) Fresh battery (I knew it needed it, old battery was over 10 years old) solved it.
It's been a while since I paid direct attention to this (I did the LR fuel lines about a year ago) so not sure while sitting at my desk here if this is physically possible but - could you have gotten the fuel lines backwards when you installed the new lines (at either end)? What was the source of the fuel leak you found last fall?
(Just trying to ascertain whether or not you were just lucky the one time you pulled the fuse and the car started.)
When it DOES start and run for those 3 seconds, does it fire immediately to life and sit at idle, or does it kinda stumble stumble sputter up to idle?
What kind of shape is the battery in? Just before I replaced the battery in mine this past spring, I noticed the car was difficult to start once it got hot. (It would start, but kinda slowly creep up to idle.) Fresh battery (I knew it needed it, old battery was over 10 years old) solved it.
It's been a while since I paid direct attention to this (I did the LR fuel lines about a year ago) so not sure while sitting at my desk here if this is physically possible but - could you have gotten the fuel lines backwards when you installed the new lines (at either end)? What was the source of the fuel leak you found last fall?
05-24-2010, 07:34 PM
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Omni,
All good questions. I did the fuse pulling trick a few times over the weekend, and I just did it four times in a row right now. It's repeatable. One time with the fuse in, it ran for about 1/2 second and then died...that was the best it's done with the fuse connected.
With the fuse removed, it does not fire to life immediately. It takes 2 seconds or so of sputtering before it catches and runs.
The battery should be fine. I just charged it three days ago and it has cranked the engine numerous times over the weekend.
I don't think the fuel lines are backwards; the return line has a hose clamp on the FPR end. I will double check. Last fall, fuel was leaking from the hard line to rubber line junction over the header. I think it was the feed line, but I'm not sure exactly.
Van,
Are you suggesting that a vacuum leak is causing the engine to get too much air? I have silicone hose to replace the vacuum lines under the intake manifold. I may give that a shot.
Swagger,
Good point, will do. Thanks.
All good questions. I did the fuse pulling trick a few times over the weekend, and I just did it four times in a row right now. It's repeatable. One time with the fuse in, it ran for about 1/2 second and then died...that was the best it's done with the fuse connected.
With the fuse removed, it does not fire to life immediately. It takes 2 seconds or so of sputtering before it catches and runs.
The battery should be fine. I just charged it three days ago and it has cranked the engine numerous times over the weekend.
I don't think the fuel lines are backwards; the return line has a hose clamp on the FPR end. I will double check. Last fall, fuel was leaking from the hard line to rubber line junction over the header. I think it was the feed line, but I'm not sure exactly.
Van,
Are you suggesting that a vacuum leak is causing the engine to get too much air? I have silicone hose to replace the vacuum lines under the intake manifold. I may give that a shot.
Swagger,
Good point, will do. Thanks.
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05-24-2010, 07:52 PM
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Moved from other thread:
Temp warning light was not on. I already ordered the seals to do the oil filter housing/cooler, so I'm going to just go ahead and do it since I can see oil leaking anyway. If I still get milkshake, it will be headgasket time.
I've already replaced the DME relay with a brand new one. Should I still do the jumper? If I disconnect the return line from the rail and try to start the car, fuel gushes out, so it seems like the pump is working. Will bench testing tell me anything new?
I hope my questions don't sound confrontational. Please feel free to educate me or shoot holes in my logic if I've got something wrong here.
Did the temp warning light ever come on? These are aluminum, open-deck motors. It wouldn't take much to cause failure, especially on an 86 951, a year with weaker head studs (improved 87+).
That said, it sounds like a fuel issue. Did you make a jumper for the DME relay? Your car sounds just like one of my 951s that had a failed fuel pump. Make a DME jumper (I believe Clark's has this, or you could just look at the relay diagram)...if that doesn't work, pull the pump and bench test it (don't run it for more than a second or so though, as it needs fuel for cooling and load). It should torque over like a banshee. The pump is external and easy to remove.
That said, it sounds like a fuel issue. Did you make a jumper for the DME relay? Your car sounds just like one of my 951s that had a failed fuel pump. Make a DME jumper (I believe Clark's has this, or you could just look at the relay diagram)...if that doesn't work, pull the pump and bench test it (don't run it for more than a second or so though, as it needs fuel for cooling and load). It should torque over like a banshee. The pump is external and easy to remove.
I've already replaced the DME relay with a brand new one. Should I still do the jumper? If I disconnect the return line from the rail and try to start the car, fuel gushes out, so it seems like the pump is working. Will bench testing tell me anything new?
I hope my questions don't sound confrontational. Please feel free to educate me or shoot holes in my logic if I've got something wrong here.
05-25-2010, 01:26 AM
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I would not try to start the car anymore until after you have drained out the old oil. By the engine not running you might not have ruined the Rod Bearings. Porsche WSM says to replace Rod Bearings if you find a milkshake color in the oil. Change out the oil cooler and install new seals. Make sure you have the alignment tool to install the oil cooler correctly for proper operation of the Oil Pressure Relief Valve or it will leak again. I put some petroleum jelly in the rubber seal slot to keep the seal in place (not a lot). Drain out the old gas and clean or replace the Fuel Check Valve on the out put side of the fuel pump and replace the fuel filter while your there. Old fuel sets up a Varnish like coating on check valves and injectors when the fuel just set there. You can also do a Compression Test to see if the Head Gasket is shot.
Cheers,
Larry
Cheers,
Larry
05-25-2010, 12:03 PM
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Larry,
Thanks for the advice. I think I'm going to do that. I have the alignment tool on the way. I have a new fuel filter ready to go. I'll drain and replace fuel, replace check valve, clean the in tank screen, and send out my injectors to be cleaned and flow tested. After I get the clean parts and new filter installed, is it wise to run some fuel / injector cleaner mix through the lines and rail to flush them out before starting the car?
Thanks for the advice. I think I'm going to do that. I have the alignment tool on the way. I have a new fuel filter ready to go. I'll drain and replace fuel, replace check valve, clean the in tank screen, and send out my injectors to be cleaned and flow tested. After I get the clean parts and new filter installed, is it wise to run some fuel / injector cleaner mix through the lines and rail to flush them out before starting the car?
05-25-2010, 02:53 PM
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Check Fuse #34. Disconnect your O2 sensor or check it if it's shorting somewhere. I read somewhere that the fuel pump and the O2 sensor wires are fed with the same fuse. Hope it helps.
05-25-2010, 04:07 PM
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Manny,
Thanks for the tip. I will try starting with the O2 sensor unplugged after I've solved my milkshake problem. I'll pick up a fuel pressure gauge to install after I've cleaned the fuel system.
Thanks for the tip. I will try starting with the O2 sensor unplugged after I've solved my milkshake problem. I'll pick up a fuel pressure gauge to install after I've cleaned the fuel system.
05-25-2010, 04:55 PM
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Yes, my thought was, on a fresh start, the idle control stabilizer will open up and the DME will trigger more fuel (to run rich like a choke) - with the extra fuel, and a possible vacuum leak, the A/F ratio is close enough for it to run. However, after the DME stops providing the extra fuel, and the idle control stabilizer shuts (or if it fails to shut), there is too much air for the reduced amount of fuel. The mixture is too lean, combustion is sporadic, and eventually the engine dies.
