papatioman

Hello all,

Purchased a 1989 C4 5.7L with 128,000 miles several months ago and having been giving it a once over. When I go to start it, it seems to crank longer than it should before starting. This is when the engine is cold or hot. I can shut it down after driving it and start it a minute later with too many cranks. I'd say its turning over at least a dozen of times. I've seen some guys on here claim that it was the nature of the beast.
Here is what I have done to try to rectify the problem.

1. New fuel pump.
2. Removed pulse dampener and replaced with a section of hose & clamps.
3. New Bosch fuel injectors.
4. New fuel pressure regulator diaphram at the tune of $70.00....ouch.

Here are what my fuel pressures are.

Key on only: Goes to 42 and then drops to 40
Engine running:38

After I shut her down after running pressure immediately drops to 30, holds at 30 for 10 minutes then drops to 0.

Since the spark plugs look difficult to get at, I imagine they probably haven't been changed in a while....will try that next.

Any other ides?

Thanks................

kleptopigdog

Weak battery?

kleptopigdog

Sorry didn't see your fuel pressures here is some reading material.
https://www.corvetteforum.com/forums...shut-down.html

LANDSHARK1

How recent is your coil and also your ignition control module under the cap?

If it were my car, I would definitely do the spark plugs next and then the coil and ignition control module if they are old or original.

Also, how old are your spark plug wires? Might be due for replacement as well, easy on an '89 L98 compared with a later LT-1!

Lastly, check and make sure that your ignition timing is set properly...that can make a huge difference as well.

papatioman

Battery is new....2 weeks old....engine cranks over just fine.

papatioman

Read the thread....I have done just about everything they talk about. Just about everything in my fuel supply system is new. Did see something about a "cold start injector", will have to check it out.

Thanks............

papatioman

I agree with you 100% as to what needs to be done next....since my entire fuel supply system is new...I was suspecting weak current to my plugs or bad plugs.

Thanks.............

Cliff Harris

Only '85 through '88 Corvettes have a cold start injector.

Your symptoms sound more like a problem with the fuel pump relay. When the ignition is first turned on the ECM turns on the fuel pump relay for 2 seconds to prime the fuel rails for starting. It then shuts off the fuel pump so it won't run continuously if you turn on the ignition but don't start the engine. The ECM turns on the fuel pump relay when it sees DRPs (Distributor Reference Pulses) from the ignition module inside the distributor. DRPs are generated any time the engine is rotating, whether cranking or running.

If the fuel pump relay fails, there is an oil pressure switch that acts as a backup. It turns on when the oil pressure reaches 4 PSI. It takes a while for the oil pressure to get high enough to turn on this switch, which is the common reason for long cranking times.

Check to see if the fuel pump relay is coming on. You should be able to hear it if you have the hood up and you're standing next to the car when the ignition is turned on. The fuel pump relay is located on the firewall between the windshield wiper motor and the brake booster. If you have a 4+3, the overdrive relay is mounted on the same bracket.

HlhnEast

I have to agree with Cliff. Check your CEL and see if it comes on at start up. Pull the codes and see if you have a Code 54 and that will narrow down your issue to electrical. The relay connector is prone to problems, wiring pulling out of the connector, insulation shrinking away, etc. Look at it closely.

Good Luck!

papatioman

Thanks Cliff....see if I can get this all straight in my head. Since with key on only I have 40 to 42 psi fuel pressure, my relay appears to work when key is turned on. You are saying the ECM shuts it down after 2 seconds due to a no start situation and re-activate once it receives DRPs and if that doesn't happen, once the oil pressure reaches 4psi it turns the relay on. This would mean it is not necessarily my relay going bad, instead the ECM is not receiving the DPRs that it should. Does this all make sense?

Thanks..................

larryp@nts-online.ne

I had the same problem with my '85. Found out that the oil pressure switch had to close before the fuel pump would activate. First I tied the fuel pump relay to the aux. power which did not work, then I used a diodes from the starting circuit to the relay.

Now when I turn the key on the fuel pump starts and will continue to run while I crank. Please note that two diodes are necessary to prevent a feed back circuit to the starter. One for each circuit.

OLP

papatioman

So I take it from what I am reading, my fuel pump relay is OK, it is not getting a signal soon enough after the initial 2 seconds of run time, so there is a delay in starting. I need to find the cause.....correct?

aDigitalPhantom

It sounds like larry had a relay problem, or a short near the fuel pump relay.

papatioman

Getting a lot of good responses here and ideas to check out. Won't have a chance to check anything out till this weekend.

Thanks all...........

larryp@nts-online.ne

The problem could be the signal to the relay or the relay could be bad. The oil pressure switch feeds the fuel pump directly.

You can open the relay cover and see if the relay engages and the contacts are clean. A volt meter will show you if the circuit is good to the fuel pump.

You can also jumper 12 volts to the fuel pump wiring to see if the motor starts faster.

OLP

VikingTrad3r

Im sub'in to this thread as i would like to see what the solution turns out to be.
My 87 has the odd long crank and I will go through all the items in this thread eventually.

VT

papatioman

Thanks Larry....first thing I will do this weekend is check all connections and put my meter on to check for good voltages. As I mentioned before, I have a new fuel pump and I have good pressure at the fuel rail at key on only. Looks like I am getting a delay on re-activation of the fuel pump while cranking due to the relay or the signal it is getting, whether it be from the ECM or oil pressure switch. I will pop the cover as well on the relay and check things out. Will post my findings this weekend.

Thanks.............

papatioman

Well the weather warmed up some and I had a couple hours this evening, so I installed a new fuel pump relay. Its a minimal cost item so I decided on a new one rather than mess with the old. I believe it may have eliminated a revolution or two when cranking. Being an old carburetor guy, I may be spoiled. A carburetor system has the fuel already delivered and waiting in the float bowl ready to be used. You can even prime an engine with a carburetor for cold starting by pumping the gas pedal, much like priming a weed eater. A fuel injection system has to deliver the fuel before you can start and there is no priming. Like I said earlier, I am giving the car a once over that will include new plugs, plug wires & coil. For all I know, since I bought the car used, the plugs may be old and over gaped. The plug wires may have lost some of their conductivity and the coil may have become weak. I have a busy weekend coming up and may not get much done on the car. I will at least pull a plug or two to check their condition. The car always starts & runs great and maybe I am expecting to much. I noticed my 2011 Ford F150 even cranks a half dozen times before it starts when cold. I will however keep working on this until I am satisfied and will post my actions & results. Thanks everyone for your help.

VikingTrad3r

well fwiw my 87 and 85 insta starts. 87 SOMEtimes takes a bit like 5 cranks. i assume it has an issue somewhere that needs to be sorted out.

i will not be stopping till they both insta start all the time like from the factory. im only saying this because i do think insta start is the normal operation condition. so i dont think u r asking for too much.

LANDSHARK1

Yes, not saying that it's not something more complicated, but in my case, time and time again, I have come up with elaborate and sophisticated higher level solutions to symptoms on my cars, only to discover that it was something really simple and rudimentary. Especially since you bought the car used and are not sure of the condition of the plugs and other components, I would definitely start with the basics (it likely needs them anyway) to set down a baseline.

I have a feeling this will likely solve your excessive cranking issue. Could be your ignition system is working overtime to overcome the excessive resistance created by your old or carbon coated plugs on a cold start. Ignition control module might be getting old and temperature sensitive on its way out too, although I believe that is usually more heat-related.

Keep us updated!