User 52121

Ok - I did a search. I read through a bunch of threads. The hard start threads I read all make sense for their symptoms. I understand some of these cars are just a little bit harder to start than others. However, what I'm experiencing I think is a little odd so I'm curious to hear others' thoughts.

Cold start - car fires instantly. Whir-whir-vroom. Sometimes just whir-vroom.

Hot restart - car also fires instantly. Whir-vroom. This is if the car has *just* run (either cold and a quick restart, or hot), any time within ~5-10 minutes of running, it will restart instantly.

Warm restart - this is where it gets weird. If the car has been shut down for ~20 minutes to a few hours (say, long enough to run into a store quick, or long enough to eat a meal at a restaurant), I have to crank the bejeebers out of it to get it to start. We're talking around 10 seconds of cranking to get it to start. People in parking lots look @ me funny. It's *only* when the car has sat for longer than 20 minutes (but not overnight to where it's cold.)

I can't think of anything in my experience that would cause this so I'm confused. I figure, if it's a fuel pump, I would have to crank the hell out of it ALL the time. I figure if it was a problem with fuel pressure draining too quickly (like say an FPR issue) then the only time it would start instantly is on a hot restart (but definitely not when cold as the fuel would have plenty of time to drain.) If it was a heat issue (say a relay or something was getting hot or maybe the fuel pump was overheating) then even a hot restart (restarting within a minute or two of the car running) would be a problem. But it's only when the car sits for a short bit. (Fuel level in the tank also doesn't matter, which would probably eliminate an overheating pump, assuming the pump is an in-tank unit.)

All I can really think of would be, perhaps, leaking fuel injectors (?) If the car sits for a little while, they leak and puddle fuel in the cylinder, creating a super rich condition and making it hard to start. If it sits a LONG time, the fuel evaporates. But then I might also expect some black smoke on a restart (which it does NOT do.) The last oil change also, while the oil was dirty, it did not smell like fuel.

Any ideas? Am I overlooking something that's common on these cars?

quinnfiske

There is a check valve on the fuel pump for holding pressure in the system. It screws into the inlet of the pump and is about $15 or so. Might be a place to start.

Rob

Leaking fuel injector. Fuel injector leaks fuel into cylinder and causes hard starting. Next time you get into this situation, try holding the gas pedal floored to clear the slightly flooded condition.

Grandpa#3

OK, The fuel pump is located outside the fuel tank, aft of and inboard the pass.side rear tire. There should be a shield cover that has screws to protect the fuel pump. The line from fuel tank goes to the inlet side of pump and the fuel check valve is screwed on the outlet side going to the fuel filter. The line from fuel filter goes to the fuel rail. Check out clarks-garage.com home. I hope this helps you out.

Cheers,
Larry

User 52121

Ok thanks for the pointers, I'll give 'em all a shot. My hunch is leaky injectors so I'll try the WOT start test first. If that doesn't do it, I can look into the valve... but I really think if the valve was bad, it would be hard starting ALL the time. It's cheap enough of a part though, it's worth trying.

User 52121

Update - holding it WOT to start the car when warm (so when my usual hard-start condition appears) did not change the start behavior. Still had to crank the hell out of it to start.

Does this change anyone's thought process?

I'm willing to try the fuel check valve, it's a cheap enough part. But I would think that, if this valve prevents fuel pressure from bleeding down, and it's bad, wouldn't it make the car hard to start when *cold* too?

quinnfiske

I think that what may be happening is that when the car is stone cold, The DME temp sensor tells the DME to make the mixture richer. The equivalent of a choke in the olden days. Fuel pressure has bled out of the rail after sitting overnight and the richer mixture helps the engine fire.

With a warm engine, you do not get a mixture as rich because the engine has retained some heat. So it is more important to have some residual fuel pressure in the rail. So they added a check valve to slow the bleed-down in the system.

If the check valve has gummed up and jammed like mine did, it might bleed pressure faster and/or restrict flow.

Just a theory.

User 52121

Alright quinnfiske, you may be on to something. Upon digging some more @ Pelican forums, and Clark's Garage, I tried swapping in a new DME relay (friend had one kicking around, new in box) and that didn't solve it. So I went to check fuel pressure. Car had been sitting for about 2 hours. It was still warm, and is within the usual timeframe for a hard start. I pulled the end cap off the fuel rail expecting a spray/blast/gush of fuel, and instead, got barely a trickle.

My guess is that the DME primes the fuel pump when cold, and may not prime (or not prime as much) when warm. Car sits long enough for fuel pressure to drain out of the rail, but not long enough for the DME to determine it's cold enough to re-prime the pump, and I get the hard start.

Figured I might as well just go through most of the usual culprits and replace 'em with fresh parts. Ordered a new FPR, new check valve, and new fuel filter. Hit all 3 so I know they're known good parts and it'll eliminate me having to order 2-3 times as I walk through the system. 130k on the car, if this stuff is original, it's probably due anyways.

bearone

you have a fuel leak someplace, pump/line/injector and fuel is vaporizing.

87951
95sl320 dd

User 52121

If it turns out the injectors are leaking I'll just have them cleaned and balanced over the winter. Figure it can't hurt to swap out these other parts anyways. Cheap enough.

bearone

be careful because if you keep driving without swapping, you keep diluting the oil with gas.

87951
95sl320 dd

User 52121

1100 miles since the last oil change. Oil is still nice and clean and gold in color. No fuel smell whatsoever. I don't think it's puddling in the cylinders too much.

User 52121

Damn.

I thought this would've, for sure, solved it.

Brand new fuel pressure regulator, fuel filter, fuel pump drain back valve, and DME solenoid.

No change to warm start behavior. Starts awesome when cold, drive car for a bit to get it hot, then let it sit for 30 minutes... and I gotta crank the daylights out of it to get it to start. On the plus side, when it *does* start, it seems to start with more "gusto" (for lack of a better way of describing it.) But then that could just be placebo effect, too. But at least now I've eliminated some stuff, so I don't feel too bad. Fuel filter probably needed to be changed anyways (looked original), the drain-back valves tend to get stuck so at least now I have a fresh one. Only real "wasted" money was the FPR but at least I guess now I have a spare for future troubleshooting.

Guess I'll check the injectors next.

quinnfiske

DME temp sensor? It is in the cylinder head toward the front in the intake side. Costs about $25. Clark's has a way of testing it. I replaced mine and the car ran a bit better. It never stopped it from starting however.

User 52121

Yeah I followed the test procedure on Clark's. Checks out fine as far as I can tell.