gelbza

I have a 93Z, 700R4 that is somewhat difficult to start. It takes about 20-30 seconds of cranking to get it to turn over when cold, but after running at all it will start immediately. Everything in the fuel/ignition/starting system is new, and the engine was replaced about a year ago.

My theory is that the fuel pump wiring may be causing the problem, as the wiring is original and pretty stiff. Am I right in thinking that old wiring would increase the resistance, making the priming of the pump and the pump itself weaker than it would be if new? I was thinking of replacing the wiring and connectors, but wanted to make sure this was a possible cause first.

Thanks

shoebox

I doubt it. If it was a wiring issue, your problems would not disappear, IMHO. Regardless of the age of parts, I would at least check fuel pressure (especially the initial pressure).

Injuneer

If there is any doubt about the integrity of the wires, measure the fuel pump supply voltage at the connector over the rear axle, with the pump running. Wire won't lose it's properties because its old, only if the strands start to corrode, or the strands are broken through damage.

There are other issues with cold vs hot start, like coolant temp sensor accuracy, rapid leakdown of fuel pressure at shutoff, etc. that can lead to extended starts. As Rob indicates, checking the fuel pressure is a good starting point.

gelbza

I think they may be corroded, as when I peel the insulation back the wires are striped with a black residue. My thought was that if the prime was weak because of wiring, then a cold start would be harder, while a hot start would already have the fuel closer to the engine. The fuel pump is brand new this past summer, and it was doing the same thing before I replaced it. The only thing original in the entire fue/ignition system is the wiring and the injectors, everything else is new within the last 2 years.

Injuneer

There should always be fuel in the fuel rails, right at the injectors. There is a check valve in the fuel pump that prevents the fuel from draining back into the tank, for exactly that reason. If 1) the check valve in the pump is faulty; 2) the fuel pressure regulator is leaking; 3) the injectors are leaking; or 4) the lines, including the flex line in the tank are leaking, the fuel rails will not hold pressure, and starting time can be extended. Not for 20-30 seconds though..... more like 5 seconds.

To test your theory of the reason for the failure, all you need to do is what Rob suggested - check the fuel pressure; and what I suggested - check the voltage at the pump. Seems like a better approach than guessing.

gelbza

Ok, thank you, I do intend to check when I get a chance, I was at work and couldn't get to it right then. Thanks again for the help!

TGGodfrey

I dont think your issue is fuel related. Nothing changes at the fuel pump after the engine fires up.

After the car fires up you have changed the temp of the face of the piston as well as the CC of the head. Fuel ignites easier in warmer air and parts begin to expand.

What do your plugs look like and more importantly what are you gapping them to? How strong is your spark? What do your compression numbers look like? A lot can happen in one year. If you have access to a scanner, read the ECU output on the coolant temp sensor and compare that to ambient temp, they should be close.

Terry