Hard starts in a 97 SLS

fleishman · #1 (**permalink**) 09-08-09, 03:35 PM

Good afternoon everyone!

I have a beautiful 97 SLS with 148,000 miles. Over the past few months it has developed a hard starting issues. On occasion, I can crank the engine and it will not start on the first try. This does not seem to be affected by how long the car sits at all, it starts right up after sitting for 10 days or it wont after 1 night and it will start right up hot or take two cranks right after I shut it off.

-The FPR is dry and has good vacuum.
-The fuel pressure is a consistant 42 psi with just the key on and while running. There is no significant pressure loss while sitting.
-No codes
-New spark plugs and wires last summer.
-New stainless fuel rail last summer.

Sometimes I even get a backfire, but I attributed this more to flooding as it happens on the occasions when I really have to crank it a few times to get it to start.

I did a lite tune up this weekend, changed the oil, cleaned the TB, pulled cleaned and re-gapped all the plugs, topped off fluids and did that fuel pressure test. I run 91 octane with ethonal treatment. So the car runs fantastic other than this starting issue!

The plugs have a little oil on the threads so I am assuming I have some worn out rings. The rear main seal is probably a lil leaky too because there is some oil dripping off the pan. But I knew this because I lose about 1qt of oil every thousand miles.

Where should I look next? Change the fuel filter?

HowardW · #2 (**permalink**) 09-08-09, 03:46 PM

What did the plugs look like when you pulled them out? In general, a plugged fuel filter will cause problems more at high RPM/speed as opposed to start up or at idle.

fleishman · #3 (**permalink**) 09-08-09, 05:27 PM

Other than a little oil on the threads. the plugs looked ok. A few cylinders had some grey build up but the points were clean.

Probably not the fuel filter then.. she rips at 5000rpms.

Only other thing that I didn't mention was that I had an unplugged o2 sensor (B1S2) for a while. I drove over some ice and ripped off the pigtail. But I patched that back together this weekend as well. That was the only code my car had, and now its gone.

HowardW · #4 (**permalink**) 09-08-09, 05:39 PM

Have you verified your fuel pump relay is working correctly?

**Ranger** · #5 (**permalink**) 09-08-09, 05:57 PM

Quote:

Originally Posted by fleishman

Other than a little oil on the threads. the plugs looked ok. A few cylinders had some grey build up but the points were clean.

Probably not the fuel filter then.. she rips at 5000rpms.

Only other thing that I didn't mention was that I had an unplugged o2 sensor (B1S2) for a while. I drove over some ice and ripped off the pigtail. But I patched that back together this weekend as well. That was the only code my car had, and now its gone.

I doubt that has anything to do with it, but how did you "patch" the pigtail? You cannot solder it. I believe there is a special kit that must be used.

submariner409 · #6 (**permalink**) 09-08-09, 06:50 PM

Oil on the plug threads is from the plug well O-ring seals and is of no concern. Plugs with tan or grey tips are OK. Plugs with black, fluffy deposits on the tips are either rich fuel mixture (sticking injector) or oil deposits - rings or valve seals.

fleishman · #7 (**permalink**) 09-08-09, 10:00 PM

Yeah, spark plugs are good. Not worried there.

As for the pigtail on the o2, I just spliced the wires from the sensor back into the harness and heat shrink wrapped them. Code went away. Not worried there.

I assumed because I can hear the fuel pump kick on and my fuel pressure gauge shot to 42 PSI as soon as I turned the key that the fuel pump and relay were working just fine.

Anything else that could contribute to a hard start?

N*Caddy · #8 (**permalink**) 09-08-09, 10:33 PM

I still believe is the FPR (even if dry). This is how mine started too; hard start (hot) but bone-dry nipple.

**Ranger** · #9 (**permalink**) 09-08-09, 10:39 PM

Really hard to say. All your symptoms seem to be variable and intermittent.

fleishman · #10 (**permalink**) 09-08-09, 11:50 PM

Sort of,

As for all my symptoms; there really is only one. The car doesn't always fire up on the first try.

And yes, it is variable and intermittent, but it still happens regularly.

"I still believe is the FPR (even if dry). This is how mine started too; hard start (hot) but bone-dry nipple. "

Small enough part, I might as well replace it!

I see a few options on Rock Auto. I will be getting the FPR for the stainless fuel rail. Should I go ACDelco or is Napa good enough?

**Ranger** · #11 (**permalink**) 09-09-09, 09:45 PM

Before you replace the FPR try adding vacuum to it. If you do not have a hand held vacuum pump, put a length of vacuum hose on the nipple and suck on it to draw a vacuum. If it holds a vacuum and there is no gas at the nipple when you pull the hose, it's good.

fleishman · #12 (**permalink**) 09-10-09, 12:23 AM

Ok, I attached a large mechanics syringe via some tubing to the FPR and it held vacuum just fine. It is perfectly dry while the engine is running as well.

I also checked the fuel pump relay by the very scientific method of my brother's ear to the open gas cap. It clicks on immediately and runs for 2 seconds then quits as it should. Running the fuel pump before starting the engine seems to make no difference on whether it starts up right away or not.

So if this is not fuel related.. must be spark right?

greg-sls · #13 (**permalink**) 09-10-09, 10:54 AM

Have you checked the injectors? Maybe one or more of them could be "dumping" fuel. Once the car is running, listen to each with a stethoscope (or a long screwdriver with the handle to your ear). There should be a rhythmic pulse to each.

**Ranger** · #14 (**permalink**) 09-10-09, 11:24 AM

If the injectors check out, then it pretty much has to be spark, unless there is a bad vacuum leak.

fleishman · #15 (**permalink**) 09-18-09, 07:08 PM

Ok so I finally had time to revisit this issue..

The injectors checked out just fine. I pulled them out of the cylinders while attached to the rail (also had the fuel pressure meter attached) and not one dripped a bit at 45 psi. I used my 5/8 wrench as a ghetto stethoscope once I had it put back together and all of the injectors had an rhythmic "woosh-woosh," barely audible behind the lifters ticking.

I removed the FPR for a visual inspection as well. It does not leak fuel with the vacuum hose removed while the engine idles, and it holds suction from a syringe.. But when I removed it I was able to dump excess fuel back out through the nozzle where the vacuum hose attaches. Is there supposed to be any fuel on that side of the diaphragm at all?

SO..
Injectors are fine
Fuel pump is fine
Fuel filter is likely fine
FPR is likely fine
No visible vacuum leaks

I am still getting random hard starts and occasional backfires. What else could be making this thing run so rich? Is there anything else that controls spark or timing at start up?